I guess I am wondering why the school would send him home? Disability doesn't equal "misbehaving." Is there an IEP in place that would protect him from being treated this way? The efforts made to help a child should be joint with the school and the parents - not just throw this in the parents' laps and expect them to fix it (nor should it be the reverse, of course). Having 2 special needs kiddos myself (one on the autism spectrum), if the school would have called me to pick up my kid because they couldn't "settle down" I wouldn't have - mostly because in my case, my kid(s) would have picked up on the easy out - get the school to call mom/dad.
If you don't have an IEP, please think about requesting one. While it is your job to do everything to help your child be successful in school (and it sounds like you are!), it is the school's responsibility as well. Things that were successful for us that we had in place were the "boost room," extra gym time, fidgets, and a place to work in a quiet room when they just couldn't settle down.
As far as the medications go, the one drug that helped our kid (made a HUGE difference) was Risperdal. I know that many docs consider it a "scary drug" but honestly it was the one drug that made the most difference in one of our kid's lives. He is also on Adderall XR and regular Adderall to help with focus, as well as Intuniv (also known as tenex or guanfacine).
It sounds like you have most of the therapy bases covered - we also did brushing therapy, joint compression therapy, music therapy, play therapy, and a life skills coach (which may be appropriate when he is older). Not sure if any of these would be a good fit for your son but worth checking into.
Good luck - I would say it gets better . . . it doesn't. However, it does get "different" and some days/weeks/months are easier to handle than others.