I have a friend going through this at the moment, and another friend who left a manipulator (not physically abusive) a few years back. It works out in the end. It's definitely exhausting and mentally draining, but take it one step at a time and you can do it. It's for the best.
Don't think of the what if's or go back over the past. That's just a waste of time. Move forward. Don't waste one more second feeling bad about your past decisions or laying guilt on yourself. Pointless. You did the best you could knowing what you knew, and give yourself a break. You didn't intentionally do any of this. You trusted this man because you loved him. He turned out to be a jerk. It happens to the best of us (it happened to me, I'm just thankful I didn't marry the guy). It' happened to my friends.
I agree with the ladies below - just find some support (counselor, call the hot line if you need help, etc.) or talk to your lawyer .. one steps at a time. If your ex doesn't care, accept it as hard as it is - and just move on. It sucks, but there it is. Kids do turn out well with one parent - my dad had grandparents raise him and he was a fabulous, loving gifted man. It happens. You don't need both parents to raise happy, confident kids - just a stable loving family - and that can be mom and 2 kids. It will be ok. Just make sure you're ok - and if you can see a counselor to feel supported, that would be great.
Who cares if he never forgives you. Who cares what your ex thinks or that he's 'moved on'. He's just found the next unfortunate woman to take advantage of. Feel thankful you've learned and are wiser and know better now. You're hurt, but you are wiser. Just feel what you're feeling, let it out - process it. Mourn. It is is a loss - of your marriage, your old family .. life as you knew it. It happens.
It does not mean that the rest of your life has to hurt. It can be better. Much happier and healthier in fact. It can be something to look forward to - and positive. Good luck :) I suspect it will be. It just takes a little time and hang in there. All the best.