I am so sorry you are having to endure this nonsense on such a regular basis. It has to be incredibly frustrating.
What I am going to suggest to you is this...
Try to DB yoiur little heart out like a pro for the next 2 months. Like you never have before. One thing we know we can expect from your H is more BS down the line. You've got to expect it and detach from it. This is obviously not your issue so do not personalize it. Your frustration may help you detach. Make some goals of what you can do to really DB for the next month or two and really implement them. See if after some time is put in, if he has softened his attitude and seems more open to working on the M. And if not, then you may truly be at a point where you want to let this M go.
Heather, I know you don't want to end your M. I have not figured out why you think that means you'd lose your kids other than he has threatened you with this. His words are not gold, dont be intimidated by his threats. You set out to DB your heart out, also to be a fabulous mom to the world so he can't try to use anything against you and then see if this is something he can work with or not. And if he cannot, then you just may need to get away for your own sanity. You can only stay in this position for so long until it wears you down, and you are feeling worn, as would any of us.
The more you detach Heather, the easy it will be. Because no matter what he spews out, it won't ruffle you and you can respond/behave in a calm and mature way.
H is def. trying to bait you. You are too smart for that, so don't fall for it. Focus on your own attitude, on detaching, on keeping your life on track, on spending quality time with your kids.
And the kid issue is what has got to be the worst. He uses them as ammo against you. He is interferring with your R with them. This is where I'd have a very hard time not losing it...I do understand the challenge you face everyday and I am sorry. I don't know any good advice for how you can interact with the kids to negate what he is doing...perhaps your counselor or someone here can offer you some decent advice there.
Meanwhile, I almost think you should go see a lawyer. Tell them that you are going to give it a couple of months to see if things improve, but that you want to know your status and options, esp. as related to the kids.
I'm not telling you what to do. It has to be your decision in the end. I guess though, you are at a point where you seem about to give up. And if you do, we'll support you. But I think you will want to know you gave your all first. So if that is where you are at, maybe this one last charged DBing effort will truly let you know if this is something to hold onto, or will allow you to walk away with peace in your decision.
I wish you the best, Heather. Don't believe all these things he says. Don't buy into them. He's one person, and his opinion is way off mark. You are a great person. You care so much about your kids that you have endured an unimaginable challenge. You know what that says about you, so don't let him sabotage that.