It could be a Complex Partial Seizure With the sleep issues I suggest you try to get the CPS checked out first since it's one of the hardest things to spot and fix if it's not a full blown seizure. A regular sleep study is not enough. They need to wire him up all over to a machine that will follow his brain wave patterns. Even then it can be missed on rare occasions. If he has FCPS then he will be treated with an anti seizure drug.
If he has Childhood Bipolar he will need medicationS. This will take awhile to fix up the cocktail that will work and it's fluctuating dosage. If he needs the meds they can actually rewire him so his future life will be much much better. However- these drugs need to be respected and monitored. The side effects can be unreal. Make sure they have fully ruled out FLS before they move on to Bipolar. Childhood Bipolar is the popular diagnosis these days and it's more likely to be diagnosed than FLS which needs to be ruled out.
Go to a really good Pediatric Neurologist. Drive hours if you must to get the guys that work with the hard cases.
Migraines could be a cause. http://mentalhealth.about.com/cs/familyresources/a/kidmigraine.htm Migraines can even cause the tummy aches. Abdominal migraines http://headaches.about.com/od/migrainediseas1/a/what_abdom_mx.htm
If your doctor isn't taking you seriously Get Another Doctor. If you are loathe to do that right off the bat- try videotaping one of his rages. In fact- video tape one of his rages. There may be signs of the cause in the tape that one wouldn't normally know to look for.
The drugs used to treat this stuff can be really messed up but they offer you your best hope. Read up on them as they are tried. If your child had diabetes you'd give them insulin. Don't think that these issues are any different. Feel free to contact me if you have continuing issues. I've been there and done that 3 times.
I am not a medical professional- this is just an example of personal experiences. Yeah me
A mental health clinician should make sure that there are no physical causes (migraines, seizures, etc) of the problem before diagnosing someone.