So him wanting to either date or stop hooking up is somehow contributing to the “crazy ex girlfriend” trope? Hmmm. That you personally don’t value meaningful monogamous relationships is your issue. That doesn’t mean the character Sam is possessive for wanting a monogamous relationship with the boy he likes and hooks up with.
I don’t understand “shell of what he used to be” comment. He already was a shell when hooking up and hurting girls, cause he was so out of touch with himself and lacked basic empathy that he just went around and hurt people like it did nothing to him. He also brushed people off who confronted him and his problematic behaviour, if that’s someone you look up to you’re the kinda person people should stay away from, cause you’re the problem.