I am outraged your xh allowed your son to play you two against each other. How dare he!
Your ex should have come to the house, sat your son down and gave him a lecture about "just because mom and I are divorced doesn't mean we aren't on the same parenting page. You will do what she says."
What an empowering ass.
Mighty, you have a great deal a self control. A great deal!
I have no idea how I would have reacted in this situation but I am pretty sure it would have involved a scathing email about limiting my ability to parent our teenage son--who is displaying destructive behavior patterns, probably due to recent traumatic events in his life---thank you very much absentee father who dumped his current family for a new family!
I know your ex has been a major part of your life and he is your children's father. But he is no longer your husband. This provides a lot of freedom when dealing with him.
You do not have to make him happy or "keep the peace." You didn't cause the disintegration of your family. He did.
I know this is a difficult concept to wrap your mind around since you have spent a lot of time trying to resolve a bad situation...but the situation has been (for lack of a better word) resolved. Your husband resolved it when he got a divorce.
He has defined new terms for your relationship which are: You don't have to work out anything with him if you don't want to. Your husband has been living under this auspices for quite a while and it is time you did as well.
This is what a divorce is. It means, "I don't have an intimate relationship with you anymore." What does this mean for you--in real terms?
It means: When your husband crosses the line (as he did with your son) treat him how you would treat anyone who contradicts your parenting style. If he doesn't like it: Tough.
To bad. So sad. Start acting like a real dad.
It was disgraceful the way he treated you as his wife. There is nothing that can be done about this now. But you will define the way he treats you as his ex-wife and how he acts as a father.