"I'm done trying to "reason" with stbx." GREAT! Stick to the agreement or get it changed, otherwise leave him alone. You are right, he is not going to share your perspective. You've got it!
"in retrospect it was futile"
Remember, futile is best case. The more you push, the more he will act out. Leave him alone, and rather than act out against you, he'll be left with himself. Left with himself, I'm just not seeing that his road to M with GF is a done deal at all. Could be of course, but this isn't a LTR yet even in terms of dating. They don't even really know each other. Things are going to be hard for them no matter what. If you butt in, they make you the butt of their troubles. If you MYOB, they can only blame each other. So, if you'd like to see her out of the picture for your kids sake, MYOB.
