You might talk to the Dr about giving more of the medications at night. For instance when my son was on Depakote and Seroquel we gave all 750mg of the Depakote at night along with 300 of the 100 mg of the Seroquel, and with that combo he finally slept through the night.
If that does not work, you might switch from Seroquel to something that works better for him, because on those doses of medications he should be able to sleep through the night. I do know that stimulants like Adderral made my son revved up to the point of sleeplessness, so you might also talk to the Dr about that. Also, you might look at his diet and if you have not already done so eliminate all sugar and caffeine.
Good luck - I have been there many times, and it is SO not fun! But it will get better. One time in the state of mania my son stole 20.00 from my wallet and went to 7-11 and bought 5 Red Bulls.........he slammed them all...........and was up for 2 days like a crazed madman! It was a horrible episode but now, years later, we are able to joke with him about it - "remember the time you slammed all those Red Bulls?" - and we all laugh.