What helps? Appropriate and firm
boundaries. Read
Boundaries by Henry Cloud.
You can do a lot by limiting contact to only the basics. Post divorce, that means focus on the parenting. Examples are handling the exchanges, sharing standard information about doctors, school, etc. You're not married to your ex and so there is no relationship to maintain. If he doesn't respect boundaries as described below and elsewhere on this site — and how to make them more likely to work — then you may have to seek support on the legal side, determining what your lawyer and court can do to limit interactions to only necessary aspects of the custody order and parenting schedule.
People with aggressively acting-out personality disorders typically resist improving their behaviors. Or if they behave for a while, they can easily — almost predictably — relapse into prior patterns. I think that's what's happening here. The family needs strong boundaries (and consequences) for proper behaviors. Whatever it takes.
You've been like many here who tried to appease and mollify someone who repeatedly crushed good boundaries, demanded constant ultimatums and capitulation, etc. That sort of one-sided relationship can't work, not for very long. As you found out.
Boundaries are for you, not Ex. You already know you can't tell Ex what to do or not do. You can't force Ex to do or not do something, your power is in your response. However, what can and does work (though there are limits) is something like this... .
"If you do or don't do ___ then I will do or not do ___."
Examples:
If you start blocking me from our kids...
...then I will enforce the parenting schedule, in court if that's what it takes.
If you want extra time for ___...
...then I may allow it but with a trade for equivalent time for ___.
If you try to talk about anything other than valid parenting matters...
...then I will hang up or depart.
When done right "if... then... " is powerful. It took me years to figure how to make boundaries such as these.
Oh, and since this would be a change to your behavior pattern, expect Ex to flame out with extinction bursts in attempts to make you retreat back into prior compliant, appeasing patterns. Ex may never fully accept that you will run your own life, but in time Ex ought to realize you're not acquiescing to Ex's demands as before and not push your boundaries as relentlessly.
