TRM, are you seeing a counsellor? I feel you need regular consultations with somebody who knows how to help you put your experience in a real-world context - to put it in proportion, if you prefer.
Your whole post, above, positively throbs with fear. The problem is not the power he has, but the power he has over you. I'm sure he is intelligent, well-prepared and all the other stuff you said. But he is NOT superhuman! He's a weak and frightened human being, afraid of being nothing & nobody. So afraid of 'invisibility', he only knows himself by reflection: the more power he can gain over other people, the more he feels he exists. In short, he's a bully.
Of course, he's not 'nothing' and he isn't invisible. You can remove all of his power over you and the kids, he won't cease to exist. He'll be okay; he's just a sad & frightened little twerp. When I think of your ex, going by the picture I've built up from your posts, I imagine a small, wiry creature: a snivelling combination of deviousness, resentment & desperation ... I'm thinking of Gollum!
Don't be afraid. He's pathetic. Like Gollum, though - or like a rat - he'll snatch any leeway you give him. Not because he's clever; because he feels like he must own you or cease to exist - which is rubbish, naturally. Silly of him.
You don't need superhuman powers any more than he does. The difference between you is that YOU don't think you need them! Er, so which of you has the weaker grip on reality?
Exactly
You do need firm boundaries, TRM. Don't provide rat-runs. I definitely advise writing them down. There is no reason on this earth (or on his planet, heh) why you should cower in your bedroom whilst he plays Daddy with your kids, in your house. That's a NO! You have a boundary around your house, and you have the law on your side. While you're ring-fencing yourself and your family, stop responding to his texts, calls, letters & emails. Copy them and forward them to your solicitor. YOU are the strong one here; you don't need to "prove" it. It's already true. You have your home, you have your family. Everything's in place, build a 'ring of protection' around your life.
When he finds he can't through, he'll go and bother someone else instead.
I have no idea whether that meant anything to you? Something like it worked for me, so I'm offering it. Cheers and good luck. x