Oh, how I feel your pain and confusion.
I have a SD16 and SS13 who live with me and husband full time.
My husband and I were pregnant with a bio child in 2010 and I had a premature delivery at 5 months. We lost the baby.

I TOTALLY agree with Echo, that's great perspective and advice. AND I also want to tell you a couple things:

1. After many conversations with my husband and probably lots of fights too, I was able to get him to see that if he "allowed" his then 11 year old son to continually throw a freakin fit everytime he didn't get his way and I mean get up in his dad's face screaming the way it was going to be...to the point that I was afraid sometimes, that this senerio would only progress and get way worse. Both of my stepkids RULED the show before I got here. I mean called all the shots. LONG story short- after a few painful and very stressful confrontations of my husband being the FATHER and not tolerating this outrageous behavior, laying down rules and consequences and following through, it is AMAZING the transition. A lot less disrespect, fights etc. Same with my SD- as soon as my husband stopped tolerating outrageous demands and disrespect, she got the point. For example, she learned pretty quickly- Oh, if I wanna ask my dad to let me practice driving the car, I have to treat him respectfully or don't even think about asking!!
Basically, I can attest that it works, AND I think it has to come from the biological parent initially. You back your wife like a bullet proof wall!!!!

2. The 2nd thing I want to say is even after all these changes, it is still difficult, for me, being in my marriage. Now you have a bio child, so it probably has you feeling more connected and like a family. But even respect doesn't NECESSARILY bring love, or family connection. It might, no guarantee. I guess I'm telling you this because I wish someone would have told me that a long time ago.

One more thing, there is something biologically wired inside us as human beings, I believe, to love our biological parents no matter how awful they are. My stepkid's mom has been in and out of rehab 7 times in the last 2 years, sees them but a handful of times a year. Pays for NOTHING. Their dad (my husband) has had FULL custody over them since SS was 3 months old. Basically he raised them ON HIS OWN. BM has broken their hearts so many times. Still, ask who they WANT/DEMAND to be with on holidays? Mother's Day? Their mom. Your SD will probably always feel this way about their dad, so don't spend too much of your energy here. Even though I know how FRUSTRATING and even hurtful this can be.

I hope this helps.

Should you stay or should you go..

You stay!! You made a vow to your wife..

Just like all the other posters...
You are the parent...you are raising these kids..
You make the rules...
You stand by those rules..

Children believe it or not want discipline..
Life will be hard...but who said it would be easy..