I am very, very sorry to hear about your situation.
Well, if he thinks he can manage to be a father to his children, then so be it...but there will come a time when your sons are going to want a relationship w/their mother. Sometimes, children have to live w/the runaway spouse for a while to actually get a taste of what life is like w/him/her.
You've done everything you can and yes, it's now time to get off the coaster and allow them to live together on a full time basis. However, there is one question that comes to mind...are you going to have to pay child support to him?
Unfortunately, and I hope that I am wrong, but I don't think he's going to be the type to leave you alone for long. He thrives on the drama. As for your sons, I do hope and pray that they don't follow in his foot steps and carry that anger around w/them full time.
I am going to keep you and your family in my thoughts and prayers. Continue to watch your back. I don't trust any of them right now.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.