Nel, You are so new to the MLC situation and I have to tell you, even if his mother speaks to him, it's going to still take a long time for him to work thru his crisis. That means he has to do the work.
If his mother tries to push and talk to him about returning home, he will distance himself from her as well. The less others interfere w/his crisis, the better. It's best to allow him to come to you or to others on his own. No one can fix him...only himself.
The most important thing to remember is that you didn't break him, therefore you can't fix him...he has to do that.
Keep the focus on you and your children. Leave him in God's hands.
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.