there are no easy answers to the problems you describe and no magic fixes. your household will be disruptive and disrupted--its part of the package-- you cant live in a white couch house. :)
your child will always be more difficult to deal with and he will pose a formidable challenge to his siblings.

It is always helpful to put yourself in your child's shoes and you need to understand that your child is not experiencing the world in the same way "normal" ( whatever the hell that means) people are experiencing it.
He has a swirl of emotions in his head that are difficult to twease apart. The world is intense and the stimulation around him bombarding. He is hypersensitive and he doesnt understand why you dont understand-- he feels like he is living on top of the tower of babel. everyone seems to be playing by foreign rules that he cannot translate or tolerate. He explodes or demands attention in inappropriate ways which is the signal that he isnt comfortable in his skin. he knows he is different. he cant understand how or why-- people are constantly telling him by word or deed that he is BAD, DEFECTIVE, DIFFERENT. Is it a suprise really, that he would act out even in areas which he might otherwise be able to control? His world is scary to him and sad.
And thats why you love him unconditionally and madly--& you defend him to people who dont understand.
Your child, with or without medication will always be different. he will always feel like a stranger in a strange land. But he can learn to speak polish, tolerate duck blood soup and do the mazurka...thats the goal--to help him bloom where he has been potted.