I'm so sorry, Haye, for all of the troubles you are having to deal with in this situation!
Have you done any reading over on the
Leaving Board: Family law, divorce and custody? I know it's generally for people who are Leaving their relationships, but there are lots of members over there who know a lot about Legal Issues unrelated to Divorce or Separation, and having to do with child custody, etc. Maybe they could help you?
In this situation, I know that you already realize that your children's best interests have to take precedence over anything else; it's hard when you are trying to help your Significant Other with his own troubles, and then need to be there and be the best Mom and advocate for your children that you can be... .I think, deep inside, you know what you have to do, and will be able to do it. I do wish you wisdom and strength, Haye~~there is a lot of pain in this situation