First, we want you as you are, each day. Not just jovial. You are an amazingly strong woman.
This is what we are saying (well, at least me).....because you are amazing, and wanting to get to normal, and pulling to the good in life, it just irritates me that he baites you back in.
I really don't think there is a way to interact with him cordially. He's not normal. You must accept that. Rat isn't either.
What I am saying is that you don't have meltdowns and rack your heart and brains wondering how to deal with him. You just do it silently through the law, if needed, or through extremely business-like emails. If he write you things like that, you note it and ask your L what you can do to stop this abuse.
It is NOT your job anymore to interpret, handle, run interference for, smooth over, or manage this maniac. He is an abusive lunatic. I mean every word of that. You are not his W anymore, you are another person in his world. What would someone else do, even if they did have to share something with him (like kids). How would they handle it. That's how you go.
Feel what you're feeling. Let it be about YOU. But, all the while, remove yourself from this man.
You are strong, talented, capable, and full of life. Keep repeating that to yourself. You are better than this.
