Jesus. This thread has been.....eye-opening.
I can see a lot of myself in this guy you're talking about OP. I'm seriously sorry you've gone through this. Don't take his last action with the new girl personally, it's probably yet another way he's irrationally keeping himself from being hurt by the "love of his life". She's very likely someone he doesn't care much for, and somehow, can't hurt him.
Again, I'm sorry you've gone through this. I hope it (and we) get better.