The only thing you have done wrong is to have done too much for too long for an ungrateful spouse. I cannot believe he told you that you need to step-up when you have been parenting those kids more than either of their parents. As far as tonight, if you want to drop them off, do it - but do not stay and hang out with BM and her family. Why in the world would your DH think you should do that? And honestly, if you don't want to take them - then don't. BM can figure it out or DH can find a way to get them there.

Do not blame yourself for what your DH said. He is way out of line. As a step-parent you are under no obligation to interact and "co-parent" with BM - that is completely the responsibility of your DH. You have done nothing but try and help all involved in this mess.

You have gone well above and beyond. These are not your children. You do not have to co-parent, not even with him. You do not have to do a blessed thing for these kids. Anything you do for them, you do out of love, respect & a genuine desire to help your spouse. I would let him know he has severely wounded you & these are not your children and not your responsibility.

Perhaps, your DH needs to be taught what not stepping up is. I would go full on strike. Babysit - nope not my kid. Drop offs - nope not my kid. Feed them - nope not my kid. Extras - nope not my kid. Shopping - nope not my kid. 

That man owes you a serious apology, a nice gift to make up for his faux pas, and some serious gratitude for everything you do.  

All you "did wrong" was set a boundary and made DH have to handle a situation that he doesn't want to handle.

If you can't tell, that's not actually something you did wrong, nor is it a YOU problem. It is BM's responsiblity to get the kids and have that all arranged. If she can't do her part, then it falls on your DH to come up with a solution.

You've set your boundary and said what you'll do. He doesn't get to stomp all over that because he has misplaced his anger onto you.

Your response to him needs to be: "DH, I already HAVE stepped up. The person who hasn't is BM. I told you what I'm willing and not willing to do. Do not blame me for BM's piss poor parenting and your own embarrassment for having procreated with her. I'm not doing this tonight or any night."

That was crappy considering how much you do for him.  I guess he was frustrated because he had no way of facilitating anything and he was probably more mad at the situation vs "you".

I didn't love seeing BM.. she also caused a lot of trouble for us and expense!  But, I would occasionally pick the girls up from her house if it was more convenient (It would be on the way of my 2 hour commute.. and my DH worked on the water.. and often couldn't be home until later.. and it was an hour away from BM.. when it was 2 minutes more for me to do it).

I am not exactly sure what she is asking.. is she asking you to drop them with her early?  hang out with her?  or is she asking to get the kids after the fireworks?  

My line in the sand would be not "hanging out" with BM.. but I would go to a walmart parking lot and let the kids go to her car.. I would make sure they were very "ready" to get out and go over to her quickly.. I would stay in the car windows rolled up.. and be gone once she had "chain of custody"..

Your DH owes you an apology. It is not your responsibility to facilitate drop offs and pick ups with the BM. It's the BM's and DH's responsibility to figure out how to get her children to point A and point B.

This situation is not an emergency. The children won't be at risk if they don't see fireworks. The BM can pay the person gas money to make another trip to town. It seems like her idea of problem solving is put the problem on you. 
 

Hold on to your boundaries. You did nothing wrong. 

First let BM pick up the kids at 6 pm.  Then what happens, happens. Not your problem.  You are off SK watching at 6 pm. Let DH and BM handle the rest of it.  Stop cooking and drops off picks ups.  Those kids have two parents you are not one of them.  Let DH co parent all he wants to.  Buy the way did he file for CS.  ??  BM dose not get get out of paying card becsuse she doesn't want to work.   Time to stand up for yourself.  He cares about BM more then you 

"I didn't sleep with BM and reproduce- the only ones responsible for co-parenting are you and her. I am not responsible for cleaning up your mess."

You are always wrong. Your SO will tell you are wrong and there loser EX will tell you are wrong.  The two who screw up there family are right. 

You aren't in the wrong at all. In fact, I say you go above and beyond. You are a better person than I am, dear. 

You do pick up and drop offs of these children? You take time out of your day to get them places they need to be? Then you say you are uncomfortable with this one thing and your husband blows up about it? That's unreasaonable of him, completely. If I were you, it would just be, 'I can't do it this time, sorry. Figure it out.'

I for one, do not pick up or drop off my SKs for ANYTHING. Absolutely NOTHING. We live 35-45 min one direction from where their school is, after school activities, BM house, etc. I expect my husband to deal with all transporation. I have my own life and it doesn't include ferrying his kids around, especially not if their BM is reluctant to do it. She puts them in all sorts of activities in their town and it isn't my fault if that interferes with DH work schedule; he must figure it out. Not me. 

If I were you, I would gently tell DH that you will not longer be in charge of getting them to dr apps or after school activities. He will soon realize what a lift you are doing...and if he doesn't...well, tough luck for him. 

Ugh your husband is acting like an entitled jerk. The only thing you did wrong was not do what the bioparents asked of you. They treat you like an unpaid employee and get mad when you don't bend over backwards to make life easy for them? 

Why do they get to pass the obligations of parenthood off to your but if you do the same you're shamed for it? 

More than once I have been mad at my husband because he tried to hold me to a higher standard than he would hold himself it's so unfair. 

They're  his kids. He made them. I don't care that his ex has six or sixty kids. She made those, too. Her responsibility. 

As Lt Dad said, you set a boundary and he's pissed. Oh well. Get over it. I'd start cutting off even more of what I do. 

Stop being his victim, his chore bitch, his defacto child care giver, and the Uber driver for his failed family spawn.

His choice of baby mama who does not drive and can't afford gas is not your problem.

No more of this crap.  No! is a complete sentence and a complete answer to any attempt he makes to guilt you into continuing to be his beck and call girl.

You can pack, raid the accounts, and leave with your therapist on vacation. Do it,

End this crap.

NOW!

Please. For  your own sake and sanity.

You are not the problem other than you tolerate this shit.

Than the absent biomum and doesn't see whats wrong with that? Bio mum doesn't get a free pass because she chooses to be mostly absent

your husband needs to be refreshed on that for perspective 

what you are rightfully pissed off about is that you can't understand why you need to step up more than the bio parents who legally, financially and biologically are responsible for their own kids

It's time you put on your bitch boots and let him have it, every lat detail of why he is a crappy, useless, ungrateful parent and husband and why he should be kissing your feet for the work you have put in trying to raise his kids in his place because he isn't capable of it. I would then walk out and leave him to figure out how to deal with this evening's situation and I'd go and start looking for a new place to live with my own children.

Just say NOPE

Shirking your parental responsibility,  giving the BM a  pass and dumping it all on SM!

Stick to your guns!

Where did you go wrong? You should have never been playing mommy to his kids in the first place.  You can't work yourself into making someone love you. Clearly, he doesn't.  Where you went wrong again was not standing up for yourself when he belittled you. My guess is this isn't the first time he has blantly disrespected you like that. Where you can go right at is by telling him and Bm to take a hike. The nerve of him. It's not your fault he laid down with a total loser not once, but twice. Smh. Never, ever ever let someone take their poor choices in life out on you!