@anomalocaris’s advice is right on. You have to identify the “why” behind behaviors before you can change them. He is really young to make much headway with prior conversations, but I wouldn’t stop talking about appropriate reactions and social skills. And, as you start identifying triggers, you can then start working on more appropriate reactions to those triggers (and avoid some environmental triggers, like too many kids at once…)
Ask the OT to work on social skills with him and triggers as you identify them.
I like the Social Stories books from Michelle Garcia Winner. Her Superflex series would be great for your son’s age.
My last thought is on medication. I know many parents who have adopted kids with FASD, and a mood stabilizer seems to be necessary more often than not. That’s not to say it’s necessary for your son, but something to consider and discuss with his doctor.
ADDitude Community Moderator, Author & Mentor on Parenting ADHD, Mom to teen w/ ADHD, LDs, and autism