I haven't read all the responses due to time issues. I do want to offer some ideas. Occupational Therapist (OT) can help a TON. Weighted blankets are part of what an Occupational Therapist (OT) can suggest to help him. If you can, get a copy of "The Out of Sync Child Has Fun". It has a lot of ideas that will help with his sensory needs - and has lots of ideas to make those things CHEAP. One idea that might be super helpful is a "crash pad". You take two twin size sheets and sew them on 3 sides, leaving one short side open. Then you stuff it with old blankets, pillows, stuffed animals with no hard eyes or buttons, etc... You can either sew the end shut after you stuff it or put a zipper or velcro there so you can take stuff out easily. I keep out of season bedding in there. This crash pad can be jumped on, hidden under (if you don't sew the end shut make sure they don't hide IN it), even rolled up in. My kids liked to have it wrapped around them and then have me push on the side so they were "squished" gently. I used stuff I had plus about $5 worth of used pillows from a thrift store I trust. It has been wonderful.
My other thoughts are about the zoloft. medications like zoloft are usually NOT a good idea for children with bipolar, even if they are depressed. the CABF should have a list of the medication protocol recommended for bipolar children and it should be at least discussed with the docs. MANY people of all ages who have bipolar can NOT take antidepressants of ANY kind. It is something to think about. I personally won't have a child on zoloft, esp a male. My son took it when he was 12 for about 8 months. At first he said it helped, so we thought it was good. Then his behavior started to change a LOT. He became really really angry and depressed, in a different way than before - i cannot explain the difference except to say it was somehow a "darker" and "meaner" depression than he had ever had. I finally went back through behavior journals and realized that at about 4 mos on zoloft things started to get a LOT worse, very much angrier and more aggressive no matter WHAT we did. He also HATED himself for feeling that way, which was new. He had hated how he felt, and had hated himself, but had not ever hated himself because of how he felt - if that makes any sense. It is how he explained it to me, fwiw.
Anyway, I URGE you to keep a daily behavior log and to go back over it every few weeks to look for trends like this. When he went off the zoloft things started to get much better but it took a few months.