Corri
Just kidding on the weapons post. Your conserns are quite valid and what you do now will impact him for years.
You are doing the most important thing already. You are being there for him. That shows he is loveable. Most men will tolorate insults of many kinds but never, never, never say anything bad about their mother. Ever.
1) In every Middle and High School there is a kid who has shaved since the third grade (repeated it 3 times) and who is big and athletic enough to make most smart kids miserable. For that I suggest wrestling or a martial arts that emphasises grapling. This way a boy can educate Bruno on the dangers of bullying with a lower danger of being thrown out of school for fighting. A kid who can defend himself but has lots of empathy will have more energy for positive ventures. Like getting good grades.
2) Dancing is outstanding. If you can get him some basic lessons but keep it a little on the down and low his confidence in dancing with the girl he wishes should rise dramaticly.
3) Teach him to give out sincere praise and practice to notice and give out positive comments on the little things you ladies do. Earrings, some design on the sweater, hair style and so on. We do not do that by nature but you probably already know that.
4) What did you like when you were in High school? What could a young man say to you that kept you in positive frame though the 3rd period? How did you take a man showing empathy and respect.
5) If you can teach him to be playful but still respectful that will be a good thing.
Good Luck
"All I want is a weeks pay for a day's work" Steve Martin