What should I do about my 7 year old son?

Every school day his teacher states in his daily progress report that he disrupts the class. One day the teacher called me telling me to pick him up. He threw a tape dispenser at a girl in his class. We had a meeting with my son's homeroom teacher, his science teacher and the principal discussing his behavior. I grounded my son for a week and he was not allowed to watch TV. He also had to write an apology letter to the girl and her parents. One night at 3:00 AM, the police knocked on my door stating my son spray painted a few neighbors' cars. I had to stay in his room all night to make sure he didn't sneak out. I asked my son where did he get the spray paint and he said he took it from the neighbor's garage. I didn't no how to punish him. I took him to 6 different professionals to test him for behavior disorders including ADHD, HDD, Autism, Bipolar, personality disorders such as Psychopathy, etc and they all said he has nothing. I also got him tested for allergies and he had nothing. He refuses to eat healthy food no matter how many times I place him in time out. I have to feed him potato chips and cheese doodles because I don't want to starve him. He will not do his homework. One Sunday 8:56 AM, I asked him to make his bed and he refused so I put him in the naughty chair like Supernanny does and he kept getting up till past 7:00 PM. This has been going on since he as a toddler. When he was 1 and I did not want to give him what he wanted to eat, he would eat toothpaste, dust, etc. He had severe separation anxiety when he was an infant. He says he wants to do what he wants and will never listen to me. I also have a 14 year old son and a 10 year old daughter and non of them were like that.