As I have said many times before, I believe your H is a severely traumatized person, for whatever reason, and I think it is serious, especially if his own family can see it too, even his mother (as I recall you mentioned). I think that he completely believes what he tells you regarding commitment and the like. That does not mean his POV is true, but I think he truly believes what he sees. He is looking for any little sign as proof that you are betraying him and that challenge to his control makes him hurt, angry and ready to fight.
I think pushing too much is going to only exacerbate the situation because in his eyes the stakes are much higher and more serious then even what you see. Again, that is just how I think HE sees it. So I think he is willing to fight tooth and nail over this, regardless of the outcome. I think he sees the stakes more like a life or death situation, or at least feels like it. IMO, you and your kids are all he has and he knows it. The logic of him pushing away what he loves the most is lost on his twisted thinking and denial (sure does seem like narcissism to me). I still think the only way to get him to stand down is by going through his soft side, which means you have to show your soft side.
Like you said before, he needs to control everything. That gives him comfort. I know that is an impossible position for you to live in, but I have a hard time seeing how you are going to get to a equitable situation without him feeling secure first. I know that is scary for you, but he seems to have a history of retaliating only after he thinks you have failed him somehow. I don’t recall him ever preemptively attacking you first (or am I forgetting something).
I think he is set on “breaking” you just like breaking a wild horse. Now I know that is not good, or what he should be doing, but that does not necessarily mean he is mean or evil. It does mean he has no empathy and that he is in serious need of help. The issue is how to get him that help, or just walk away. I truly think the only for him to hear you is for you to put yourself in his shoes, as you did once. Perhaps he is seeing that you went through the motions once, and now after only a few months, your old patterns remerge (whatever those patterns may be). The only reason I can see that he would be watching for this is that he is very hurt by it.
So my message is to not escalate the power struggle, and try something along the lines of what Corri posted:
I was willing to stay open with him, and I let him know what was going on with ME so HE wouldn't personalize it. I did that for him, because he was being so patient with me.
This will be hard. But you were doing so good until the both of you slipped back into the need to test one another surrounding this Vegas trip.
PS. NOP, I am offering an alternate POV for Heather, that follows on her earlier success. That does not mean I disagree with your advice.