Re: the self-injury... a friend's daughter did this until her curriculum was enriched and she was no longer stressed from boredom at school.
You mentioned your DS loves PE - what about sensory integration issues? We are looking at sensory integration disorder for my ADHD dx DS (I said SIG from the beginning and now everyone else is finally catching up). The energy that he needs to expend holding himself together during school eventually runs out and once that 3:00 buzzer rings... he turns into a hurricane some days. The key difference is that he's not aggressive... granted he's not PG either, so he's likely not as frustrated as your DS.
Anyway, the school OT recommended exercises for him to do during the day (eg. wall push ups in the hallway) and on some days he asks repeatedly to do them because they help calm him down and focus him.
