Something to consider - ANY kid, especially one with Pervasive Developmental Disorder (PDD) from my experience, who is sleep-deprived (unable to sleep for whatever reason) is likely to be a handful. We went through this with difficult child 3 when he was 5. He'd been put on Zoloft (to try to calm down some of the ADHD behaviours) and he went very strange. He seemed to improve immediately but he wasn't sleeping. As the sleep deprivation kicked in, the problems grew rapidly worse instead of better and we took him off it after about three days. But what we saw looks a lot like what you describe. And I put ALL of it down simply to difficult child 3 not sleeping.
Is there a chance this could be a similar medication reaction? difficult child 3 has a number of paradoxic reactions to medications, especially antidepressants. If he had something like that, unrecognised, and he was still on the same medications months or more later, then I hate to think what sort of chaos it would be causing in his head and in his behaviour.
Basically, continual insomnia causes the most appalling and cumulative behaviour problems.
Just a thought, anyway.
Another idea, from our local child disability group - there is a little girl we know, seemingly normal in appearance and behaviour (when she's awake) who gets really manic at times when she IS awake, and often at times when everybody else is trying to sleep. Her mother has been frantic for answers, literally for years - they finally found out this little girl has SEVERE obstructive sleep apnoea, she's scared to go to sleep because she's constantly suffocating and has appalling nightmares. When she DOES sleep, though, it's almost round the clock and she can't be roused. Very scary.
In this little girl's case, her tonsils aren't in good shape (and hence hr adenoids are probably not good either). When they looked at her adenoids they found they are seriously enlarged, contributing to the obstructive airway problems. I'm not saying your son has this, or even to the same degree, but it could be another contributing factor.
Is there a sleep disorders clinic you could contact? You can't live without sleep. Neither can he. This is urgent. You need help and I don't think it's Residential Treatment Center (RTC) that you need, at least as a first port of call.
Good luck. This is a nasty one.
Marg