We hear you.

You and hubby have to get on the same page. Step life is seriously hard, and if you and him can't find a balance between his feelings and yours it will break you. Learning how to talk about things and really work with you partner as a team in coping with difficult situations will make it easier. My hubby always jumped at any extra time he could get with ss, but he talked to me about that before hand and made sure I was agreeable to that plan. he delt with the work of parenting and insisted his son treat me with respect. You are not selfish. You are also not a doormat. You and your partner need to set clear boundaries about how your family will function and stick with them. He needs to respect your limits even if they're not what he wants to hear.

I'm sorry, it's hard and it's a life laced with guilt trips, insecurity, and self doubt. 

So far you haven't pointed out anything "amazing" about this man, other than he is amazing at dismissing you, not listening to you and not treating you like an equal partner in this relationship.

The best course of action in this is to not change YOUR plans just because he decided to see his kids last minute. YOUR life doesn't have to stop just because his does. If he asks why, you explain that you're giving him the same courtesy that he gives you, and since he doesn't want to communicate with you about it, you're interpreting his lack of caring as permission that what you're doing is fine. He can't have it both ways.

Also, it's much more empowering to realize that your DH IS part of the problem versus putting it all on BM. He SHOULD have had a court order (CO) before you came along. He SHOULD have been talking to an attorney years ago about setting up visitation. He SHOULD have had all this sorted and a consistent schedule in place before moving on with someone else.

He didn't. He has focused on finding a new wife, getting a new house, etc than getting HIS personal life and baggage in order. It is unfair to ask you to shoulder ANY of the responsibility and chaos HIS lack of preparation has caused.

That's not to say I don't empathize with him. I have a lot of empathy for fathers in the family court system. It's not fair how difficult it is for them to have even basic rights and privileges. I wouldn't look down on a father who was only granted EOWE in spite of trying. However, you're in a situation where your DH hasn't tried, hasn't sorted this out, and likely was fine with the way things were until you came around. And it's not because of chaos that he's addressing this; it's because he can offload some of the responsibility off to you. If it weren't that, then he would have talked to you about what you want for your mutual household versus just ramming through what he wants no matter the expense to you.

So, right now, keep your plans even if they run counter to what he wants. He'll either learn that he needs to communicate with you OR he'll resent you for not being at his neck and call. If it's the former, you can work through it. If it's the latter, you'll know that part of your attractiveness to him is your usefulness to him, and that hurts to find out.

Welcome and good luck.

He is just so amazing.  Drops you for his kids.  BM control him.  I hope this amazing man. Cleans his dirty kids, cooks and cleans up after dinner.  That you are not the hired help, and babysitter.  Bed warmer. 
AsLong as BM control everything, it's only going to get worst.