Oh my love, after reading the first few pages I felt I could write the script for your useless ex. So predictable.
All those who have said that he flounced off to punish you, and has now put himself in a corner he can't get out of are right.
You are not playing the role he wanted you to OP!! You should be grateful to have him back, and actually apologising for over-reacting! That's what he wants now!
You must, must, must get proper legal advice. You must detach from him and his family completely, whilst ensuring that the kids still have contact with him. Everyone knows the truth, even if he lies to them and they go along with it. They know he's a twillock, he knows it, we all know it. That's what he can't handle.
I know what he will do next - because, although I wasn't in your shoes exactly, and my circumstances were different, I caught out my cheating husband of 20 years, and booted him out, and he sounds very similar to yours. He will try to re-write history, he will make out that your irrational behaviour made him act like this. He will try his hardest to justify what he's done. Ignore it. It will say far more about him than it ever will about you. Everyone knows he's buggered this up; he knows it too, deep down, so he'll kick off now, and spit his dummy out. Let him.
You'll be fine.