Help me understand something. The first "bomb" was when he had an A with another woman and now he's having a pseudo EA with the XW? As I've said before, I see a pattern of not being happy with whoever he is with, a pattern of always striving to get whatever it is that he needs but never arriving.
I think my H might be headed that way. I certainly don't want to be the XW he calls in 5-10 years after being married to someone else and even having children with that person!!
Great idea to stop contacting him, and I would explore your idea of moving closer to your family. Now, you've got to be prepared to end your M. Are you really ready? What about not having any contact at all with him (except to let him see the kids) for 2-3 weeks and then see how you feel?
I can't tell you what I would do in your sitch bc I don't know all the details and bc I'm not you. Only you know.