I am sorry that you continue to have to deal with a person that has caused you so much pain in the past. I am glad you see that it is HIS deficit, and nothing to do with you personally that makes him act the way that he did toward you.
For whatever reason your ex sounds like a man incapable of having a successful romantic relationship as made clear in not only his treatment of you, but from what you have heard about
his past. I applaud you for getting out of the relationship when you did!
From here on, you need only to have a business type of relationship. Co-parenting can be very personal, with the two parents working together closely as partners...but in situations where an ex is toxic, it is perfectly alright to keep your interactions with him brief and strictly matter of fact.
Someone can only hurt/belittle/abuse you with your permission. Don't allow him any more power over you than he already has had in the past.
No longer tell him anything of a personal nature, keep the small talk brief and general...and if he tries to say anything nasty to you shut it down. You could reply with, 'Do not continue to talk to me like that, I will not allow it any longer.' If he tries to persist, hang up, walk away, and basically disengage. Arguing or replying just gives him leverage to continue the harassment.
It may take a few tries and some time to break the old patterns of how you interact. However, if you persist with the zero tolerance of disrespect, and set the boundaries for YOU to dictate how the relationship/interaction is going to go...he will eventually have no choice but to comply with YOUR rules.
Don't view yourself as the victim....make yourself the boss!
Best to you, and continue posting with us for support.
"Courage is not the abscence of fear, it is feeling afraid and doing it anyway!"
"Worrying does not empty tomorrow of its troubles...it empties today of its strength."
Corrie Ten Boom
Panic Syndrome recovery due to CBT