I think just your presence and you letting him know that he can talk to you about ANYTHING he feels, even if he's mad at you (which can actually be the case - because it's safe to be mad at you, you didn't leave him), will be a good start. Let him know you will not leave him no matter what. He is probably very insecure. And as much as it kills you, try to play down Daddy's absence. This is the suckiest part of all this crap...
Anyway, when you see the counselor, try not to be defensive. It's natural to feel that way I think, but try not to.
It sounds like S10 is involved in some good things already. He is probably one of those kids that takes everything in and processes it internally. My son is that way and it's not necessarily a bad thing as long as his needs to feel secure and loved unconditionally are met by his primary parent, which is you.
