I know your story well, lived some of that. I still have to talk to my ex about our son and she still loves to fight. I do not give her the satisfaction and every time I hang up the phone I have a huge smile.
I’ve actually come to articulate what my fighting style is: The angrier I get, the more I go into “Mr. Spock” mode. And my attitude is, if I lose my cool, I’ve lost the argument. My ex actually tole me one time that by not getting angry I’m proving I don’t care. FWIW, her parents fought all the time and mine NEVER did. My current wife’s parents never did either. They loved each other like crazy - and definitely took on the roles and responsibilities in the marriage associated with their sex. As do my wife and I. And we both love it.