No, no, no, don't give in now.
Write a list of all the horrible stuff he did, and look at it every time you weaken.
Write another list of all the good things about being away from him - not having to wash his clothes, control over the tv remote - it doesn't necessarily have to be the Big Stuff.
Spend some time fantasizing about your future. What kind of life do you want have, and what steps do you need to take to get there?
Every time you find yourself fretting about how he feels, remind yourself that this is not your responsibility. How do you feel? Stop looking after his feelings at the expense of your own.
Look at your ds, and imagine how you'd feel if he grew up with this example of a relationship, if one day you saw his gf crying because he called her a fat bitch, if she walked away from him with their dc because of it.
Listen to music by women about leaving relationships because they're no good (nothing wrong with a bit of Beyonce - The Best Thing You Never Had, Irreplaceable).
Another thing that helped me - I knew deep down that I'd end up having to leave again, that even if he was good for a while, he'd relapse into his real self. The idea of having to do that horribly difficult feat of leaving - it was easier to stay left the first time.