FWIW remember he is trained to manipulate people by TRADE.
Try NOT answering any mail from him for 48 hours. Even mail about the kids can wait 48 hours. If it is an emergency his lawyer can call your lawyer who WILL call you.
Just try 48 hours NO response... and see what happens. Hell.. it's only 48 hours and it is merely silence you are offering.
Let us know what happens and how he reacts. I am willing to bet you will learn something. If my bet is wrong, then we all will learn something. Either way what is learned will be good.