Just a few more suggestions;
1) If he ever gets physically abusive (pre- or post-break-up), tell as many people as you can about it. Go to the doctor, have your injuries documented.
2) Keep a detailed diary of the contacts he makes with you and the kids. Don't talk to him over the phone unless you're recording or have him on a speaker with another adult present. Save all messages, be they e-mails, IMs or texts. Note especially his (lack of) contact with the kiddoes - it will give you ammo if/when there is going to be a custody hearing.
3) Look into support groups for people who have been victimized by people with personality disorders. They might have bunch of good advice.
4) Never show him fear. I know of a woman whose partner was telling her that if she ever tried to leave, he would file for custody and bring in character wittnesses who would confim she was sexually immoral, a bad parent, a substance abuser and mentally instable. She responded with; "Oh there's no need for that. I'm okay with seeing the kids every other weekend. Just decide if you want me to pick them up on Thursdays or Fridays". He never brought up the issue again.
Me: bi female in my twenties