As still_crazy mentioned, Seroquel can be extremely sedating. I can vouch for that; we have played with the dosage for a while to get it balanced between symptoms and sedation. That being said, it may work for him!

Extrapyramidial side effects (EPS) such as akathisia is another thing you'd want to avoid. Trust me, it sucks. I did not have it with Seroquel, but did experience it with Risperdal to some extent.

I definitely agree with still_crazy though. Maybe one of the obove mentioned things (gabapentin, Lyrica) could be of some assistance?
Lamicatal seemed to work for me, but I know that it can be unpleasant and they will (are obligated to) warn you of a possible skin reaction, which may sound scary, but a good doctor tapers up very slowly!
(in my case, increasing 25 mg every two weeks starting at 25 mg)

Hope you have found some clarity in these responses!