I am in no position to say leave as I am currently struggling with my own dilema debating if the pain and struggle is worth it for my marriage but I also have no bio children. Buuut I am the same age and I can say we have a long life ahead and if you are not happy now, there is a good chance you wont be in the future. You have a child to think about. You need to do what is right for her and if having a split home where she can have possibly 2 happy homes, is better than living in one where the father is unhappy. Do what is right for you and her. If need be, find a lawyer that specializes in family law for the fathers rights!

I feel bad for you - this will not be an easy break-up. You will become The Enemy and she and her father will go Scorched Earth on you.  Do a lot of research first on the best way to do it - make sure all of your important papers are out of the house first. Don't tell her, have a plan in place and then execute it. Find an attorney who understands Borderline Personality Disorder. Record some of those fights so people can see how she acts.  Take your time and do it right.

In the meanwhile, rehome the poor pooch. 

You really need to start talking to a lawyer to see what you need to do to get out of this relationship and retain custody of your daughter.  Then maybe a therapist or some books to teach you how to constructively deal with your wife’s mental illness, so she doesn’t end up bringing you down with her.

Go get legal advice. Don't assume you can't get custody if you haven't even asked the question. A lawyer might have other suggestions for mitigating the situation .

Please take the dog to a shelter. The dog has no one to protect it and you stand by and allow someone to abuse it. That is neglect. That dog depends on you to keep it safe and protect it. It cannot save itself -- you must do it. When that dog bites, it will be euthanized. Do it a favor and take it to a shelter so it has a chance.

I'm so tired of being in this situation. We fight  a lot, over sd, who's behavior presents a danger to our bio kid. I cant stomach living with sd forever. When I think about it, I shudder. I'm currently planning my move.  Like you, I've hesitated so much because I dont ever wish my kid to be around sd unsupervised. Sd is too unpredictable and aggressive. I worry so much that SO will get my son on his own time while sd is there. Talk to an attorney about your rights and what to do. The other thing you need to think about is being locked into havi g to live near your stbx because she lives there for her daughter and family. Ugh. Same shit I think of. My support and family isnt as far as yours but whenever I think that I could get lpckedninto having to stay close by just because so is already locked into his agreement custody with his ex wife, it sickens me. I hate steplife so much. 

Definitely go see an attorney. Keep getting all the proof you can that you would be the better custodial parent. Wife work hours, SD poor behavior that is not addressed. 

Woah!
You LET your SD "kick the ever living crap out" of  your dog?
Rehome your dog ASAP because you letting this happen is completely disgusting.

While  you are at it, rehome yourself.
This situation is toxic and your child spending any more time in this situation is damaging.
If,  as you claim,  you have evidence of the bad behaviour of your wife, SD and her family, use it in your case to get full custody of your child.
Staying only makes things worse.
 

If you let bring this up to her will she go WW3 on you? 

All great advice above.  Adding to the chorus of please rehome the poor dog!  It is truly innocent in all this and should not have to suffer this.  Unless the poor thing is with you 24-7 you are simply not able to protect it.  The fact you are stopping the beast of a step daughter when she attacks it should be proof enough.  You are reacting to and not preventing the poor thing’s pain.

So what changed from earlier this week when you said you loved her and were okay with what she was doing with her daughter and you were cool being the guy who was hands off. Just taking care of your daughter and that you were able to compartmentalize the three different dynamics to their own spaces?

You played it that you had all the ammo you needed against your wife that you love very much and would win hands down in court against her with your BD.

I guess I'm just wondering what was the monumental shift that suddenly happened that you are no longer cool with all this and no longer love your wife so much? And worry that you don't have enough ammo to win hands down in court?

As everyone above said- start with lawyers. Go through several consultations to find the best bulldog you can possibly afford. 

See if you can find any firms that specialize in father's rights. You are going to have a fight on your hand but if you can prove all of her behaviors it might not be as big as it could be.

It's a huge risk.  You would most likely get 50/50 or less.  And your psycho SO would treat you the same way she is treating the other father.  Your life would still be a nightmare and your child would have no protection from her BM.  If I were you I would placate and bide my time for as long as possible.

A legal battle will cost $30k+.

Whatever you do - DO NOT START FEELING BAD FOR HER, or at the very least, if you do, don't let it stop you..  Even if you love her, you have to recognize that she is dangerous to you. Very dangerous. Any evidence you can get of her behavior, the better chance you have of getting custody. Keep videotaping. Make a log of the time you are parenting your daughter. Start moving everything you value out of your home to a trusted friend's house, or something of the sort. Anything you leave there, you will never see again.

Plan to take your daughter and the dog when you leave. They are just as much yours as hers, and many men make the mistake of leaving the kid there, and then it's hard to prove that you fear for your daughter's safety, when you left her in the mother's care.

Just plan very carefully.

You need to stay for your daughter (& yes, the poor fur baby too!). Any attorney will tell you NOT TO MOVE OUT, but to stand your ground, and prove your diligence in protecting your daughter. I know, given the circumstances, it's tough, but stick it out.

Your wife needs to be medically evaluated, and you need to have proof she is not stable, medically. No judge or attorney will just go on hear say, they want and need facts to present to a judge.

Be sure to document the long work hours she is away, even when she doesn't have to be (that can be construed as neglect). Also, document when the other child is cruel to the dog. Studies have proven people "practice" abuse on animals then move to people to abuse.

You mentioned your family is 8 hours away. Are they in the same state, or a different one?

There are legal advisors online. You could start there, and ask for a referral. You definintely need an expert family law attorney. I have seen dads sue for full custody and win, making the ex pay child support.

Good luck. I'm pulling for you and your daughter, and your dog. PLEASE, PLEASE, PLEASE, reach out to rescue organizations or no-kill shelters to try to find a better life for this pet. The pet deserves that.

How could you love her after she talks like that to you?

when you leave make sure the child is physically with you. This will work in your favor.

make sure all your divorce and custody paperwork is ready to file

save enough money in a different account to pay your mortgage until it sells in case she makes it impossible to get money from her to pay the mortgage during the separation. So as not to ruin your credit.

take your name off joint accounts and jointly owned things like cars bank accounts  phone account and insurance policies.

file a restraining order on her and list the child as another party she has to stay away from 

none of this will guarantee you custody but it will buy you time.

The challenge you are facing is whether or not to remain with his woman and sacrifice your own life in the chance that staying would help to protect your daughter from her own mother.  Or do you roll the dice on getting full custody and leave to raise your daughter with limited exposure to her mother.  

Tough call.

Good luck.

if two unhappy parents go their separate ways instead of seeing them fight/ argue/disagree. Life is short. Do you and your child a favor and save yourselves... 

Get in touch with a father's rights group/association. They shoud be able to advise you on the best lawyer for your situation in your area. 

Even with clear evidence of parental alienation mums get off scot free. In some jurisdictions judges are still willing to allow a kid live primarily with bio mum who is a heavy drug addict actively high and having strangers crash in her home high and the courts say that a mum there is better than putting that kid solely in responsible dads home.

its a shit messed up system but keep your documentation and evidence. My husbands ex married days after divorce was final and turns out she’d been with her ex high school sweetheart whilst still married.

her 3 kids are still upset the divorce had been finalised barely days prior and she gets married whilst the kids were at school and she waits for them home and says “i got married while you were at school and you have a new daddy”, she was on a mission for revenge against her exhusband divorcing her and sought out to alienate her kids

I've been wanting you to get out for a while. First, get the the dog out. Now. Then, work on your next plan of attack. Get out, get out, get out. 

Unfortunately, it is going to be tough to prove the PA.  It has a big risk of looking like bitter EX'es picking on the poor defenseless woman.  Another poster, I think, had this thought.. and it didn't work out well.

It's also unfortunate that when YOU become the enemy that she will cling to your daughter as a prize.. just as she has done with her other child.  Just because you have been doing the lion's share with your daughter doesn't mean that she won't lay on the injured party act in court.

If you can document abuse or neglect in your home.. do that.  If you can document her working hours.. do that.  Get your financial ducks in a row.. quietly.  Seek legal counsel immediately. 

I understand the dilemma of wanting to leave but being afraid the unstable parent will get custody. If you stay, you can keep eyes on your own child at all times and its nerve wracking to think the unstable parent may have time with the child when you aren't there to protect her. Its one thing when you're just not happy together, it's a whole other thing when you are AFRAID to leave your child with the other parent. I get it. I finally filed for divorce last week and am planning to file for full custody. I just pray that the judge sees the danger my daughter could be in if DH gets unsupervised time. Anyway, back to you. You absolutely have to go speak to an attorney. Why not open a separate bank account and change your direct deposit to have a % go into the separate account. Then eventually you move everything to the separate account. Also, like others have said, the dog really needs to go to a home where he can be protected.

I have a question:

In your opening paragraph, you said the following:

"Her child is misbehaved and messed up to the point that I don't want our shared daughter around her, and my wife and her family fight tooth and nail every single day about it."

Can you elaborate more on the fights your wife has with her family?

When your wife assaults you please call 911.  Police will file charges on your behalf and also she will be charge for assault in presence of minor. SHE should be carted off in the paddy wagon.

Go to all hearings and file for full custody right away.

I could share stories but we are only talking about you.

BE safe and be very careful she can easily turn this around and call the police saying YOU assulted her.Happens all the time.Then your booted out of the house, in jail and she files for full custody of your baby girl.

1 in 9 men are assulted by women.

I know 3 men who were assulted by their wives.

One more thing. Are you aware the when kids harm innocent animals it is a HUGE red flag to Mental Health providers.

Move to Texas and bring your footage with you.   Recordings are admissable and it is not required that any party be notified if you are recording others you are interfacing with.

We used this to counter my SS's toxic SpermClan.  The SpermClan tried to invoke legal consequences for us recording them when they called with their crap.  Nope, we live in Texas and can record our own conversations, etc... without notifiying them.  The SpermLand judge told them there was nothing he could do about it.  We kept the recordings to replay when they lied and kept the threat of change of venue to Texas.  Once a minor is resident in Texas with a parent for 6mos venue can be changed and the CO adjudicated in Texas Vs the original state.

At least that was the guidance from our Texas killer shark attorney 22+ years ago.