Can I suggest a few things you can tell him?
1) He's not alone.
2) It wasn't his fault.
3) An abused boy doesn't just "get over it".
4) There is no shame in feeling hurt.
5) There is no schedule or timetable except his.
6) You are there for him whenever he is able to talk about it, and so are we.
My first thought is don't campiang with him. Just let him know these points and keep it simple. Let him see the door is open if he wants to walk through it.
Nobody living can ever stop me
As I go walking my freedom highway.
Nobody living can make me turn back:
This land was made for you and me. (Woody Guthrie)