... but it sounds like his anger is a form of depression. Classically, people tend to think of depression as an inward-turning sort of thing where a person withdraws. But in males, depression can be masked by anger.
I can sympathize with trying to find services for your son. Society is only beginning to understand that sexual abuse of males can be just as devastating as sexual abuse of females. Look at the wildly differing sentences handed down to female teachers who sexually abuse male students. That's a symptom of the schizophrenic way society views sexual abse of males by females. On the one hand, we are extremely concerned about protecting little girls (and protecting boys from male predators), but there is an undercurrent of "hey, what a stud!" when an underage boy is molested by an older female. Remember the movie "Summer of '42"? Most people view it as a romantic movie, but from a legal standpoint, it could be considered statutory rape.
You know your son better than any of us on an internet message board, so in the long run it's up to you to choose to kep him close. At some point he will be out on his own and the best you can do is to prepare him as best you can. You might try reading up on the subject and educating yourself as much as possible. A good starting point is the book Wounded Boys Heroic Men: A Man's Guide to Recovering from Child Abuse, by Daniel Jay Sonkin. Here's an amazon.com link to it:
http://www.amazon.com/gp/product/1580620108/sr=8-1/qid=1145210008/ref=pd_bbs_1/102-7080085-7028159?%5Fencoding=UTF8I wish you all the best of luck. Recovery isn't easy and it's next to impossible if the victim isn't ready to deal with what happened to him. Let him be the one to decide when he's ready to deal with it. If you force him to confront feelings he's not ready for, he'll resent you.