D, I'm glad to hear your son is getting help. If they aren't able to help him though, I hope you will consider reporting your X to child services. It sounds like if nothing else, S11 is being emotionally abused and who knows what else from the comments he made. The whole "if you knew what's been going on" comment worries me.
I think it's a really good thing he has you to confide in and help him out. I'm sure a lot of kids don't have that, and then what happens....