New and in need of advice

Hello everyone, I have finally got round to joining this forum on the advice of my sons consultant. My son is 7 and was diagnosed quite quickly during his first year at primary school. Until this point we just thought he was quirky lol. He is high functioning and does ok at school, struggles to form friendships with his peers but has really good relationships with teachers and us at home as well as an amazing bond with his two younger sisters. He has problems sleeping and is on melatonin to help with this.

I have 2 questions really, the first is regarding his sleep issues. at his last appointment he was taking 4mg beforw bed, we advised that he waa now going to sleep with very little issue but was getting up everyday between 2am and 5am this was for the whole day he would not go back to sleep until following bed time. We have now been told to increase the meds by 2mg every 2 weeks until he is on 10mg. He is currently taking 6mg and goes to sleep faster at night but it doesn't seem to have helped him stay asleep. He is still up at silly o clock. Does anyone know if this will improve with the increase in meds? 

Secondly, he has begun in the last 3-4 weeks suffering from rages. The smallest thing can set him off. He then is like A whirlwind screaming throwing things and last night bashed a hammer down in inches away from his sisters head. Today when I went to collect him from school found him being restrained by a teacher due to trying to lash out. Apparently someone had knocked him with either a chair or table and he justs went loopy. he then ran away from me and refused to walk home. It took me telephoning his dad at work to talk to him to get him to move off the playing field. These instances are becoming increasingly common and I just don't know what to do anymore. 

I have his sisters who are 5 and 3 to think of as well as a very unexpected pregnancy which is taking its toll. I have no help with him other than weekend when daddy isn't working. 

Me and hubby have decided that we will so our best to not treat him any differnet from his sisters , we are trying to raise a little boy who will function perfectly well in society on his own and be independent.

If anyone managed to get through my story well done and any advice would be welcome. x