I am so sorry that your sons are having a difficult time w/this situation, a situation that is not of your making or theirs. Therapy will be a safe place for them to talk, vent, express their anger and concerns.
As for your h, I'm glad you stood your ground and set your boundary...now you need to stick to that boundary and do not waffle on it.
Your h is still trying to control the home situation...poor man...he can't see and/or accept that he doesn't have that control any longer. He gave it up when he walked.
I think your h isn't happy w/what the lawyer is advising him that he can and can't do. I have this feeling, like my xh, he's going to go through a couple of lawyers before this is over with.
The article that Wonka referred to is very good. Take the time to read it.
I hope that you and your sons have a good week. I know it's tough to watch your children go through this painful journey, but I also know that you are an excellent mother and will be there for them and ensure that they get the help they need to navigate this situation.
Sending positive and warm thoughts your way.
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.