I wouldn't even begin to know how to help a kid that young rebuild his world after something like that. I really feel for that kid.
I think there are a lot of boys who were sexuall abused, who are now men and walking around with a lot of pain. It's pretty sad. Actually, a boy in that situation would best be helped by the presence of a strong sensitive man who knows the real meaning of boundaries. Maybe he'll know a little psychology too, as what happens with fathers of boys who have been sexually abused they worry about the boys turning gay.