Looks like he's getting the best of both worlds. A little bit of L bomb here, a bit of puppy-dog 'meant to be' rubbish and you'll give it up before anyone can say 'but what about the other girl?'
You're not only degrading yourself every time you give your (should be) precious time to him; you're doing a disservice to this other girl, who's abusive history you tell us as if to say that he should be taking that into account - well, why aren't YOU? Put your behaviour where your mouth is and stop being an utter prat for this guy. I know you secretly looooooove the thought that he's choosing you over her (because that's what true love is all about), but in reality, the only person he's choosing is himself.
What next? When he gives it the ol' Justin Beiber baby baby ooh treatment, you'll go running. Yes you will. Like road runner, whoosh! So it doesn't matter what we say. I just want you to be aware of how everyday Jim would see your situation (and does: bet you've got a rep in the circles you road-run in).
But, in the name of maybe-I'm-wrong-and-she-really-does-want-to-change-for-the-better-instead-of-expecting-sympathy...
1. Put the violin away. If he's so howibble then why are you bothering? Makes you a bit of a turnip, dunnit?
2. Get rid. No FB, no phone number, no bithday text, no 'how are you', no 'let's have an emotional talk (and get naked nomnomnom) - NUFFING. Drop him like he's hot and if he texts you saying 'y wots up bbz', tell him you're upping your game and therefore can no longer accommodate little ****s like him.
3. If you really want to demonstrate better qualities, tell the girl. Yes! Flipping well tell her that you were stupid to do it but you've been sniffing around her guy and you're sorry. If she doesn't believe you, well, that's her journey. But tell her because you owe it to her.
.. You gonna do any of that?
Nooooooooooooo 'course not. 'Cos that would require balls.