I know this pattern all to well, I get it. He needs to feel he won and he can’t converse unless the conversation goes in the direction he wants. His change from being argumentative to loving is showing you just how inconsiderate of your views and opinions he can be. This is behavior that is engaged by a child, not an adult. He is pushing your buttons to mother him.

He is not a parent, everyone walks on eggshells around him, including you. He probably creates this dynamic in work environments too. That’s why he ends up getting fired.