I'm glad that he's agreed to therapy...but don't be surprised if he comes back after the 20th session and reminds you that you need to sign the papers. (I hope that I'm wrong about that.)
I'm keeping you and your family in my thoughts and prayers and hope that the therapy will help him. I hope that he wakes up enough to realize that he needs to be at home w/you and the boys.
For now, listen, validate and just be a friend to him. If he wants to talk about his therapy sessions, then listen, but don't offer advice.
Continue to keep the focus on you and your sons. Allow the man upstairs to do his work on your h.
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.