I had a boy just like that....well, I still have the boy, but he's a much more mature 9yo now.
We tried everything, too. I did a behavior chart for a while. I was careful how I made it, though, because I didn't want to make it seem like the behavior was optional, know what I mean? So I listed attributes like "honesty, patience, kindness, etc." and he got a sticker when he displayed that character quality. We also set up goals and rewards....of course we started with something easily attainable to encourage him right off the bat. It worked for a time but he got bored with it, too. He is also very bright and strong-willed and he can only take the rewards we were offering so long before tiring of the whole thing.
Later we decided that he needed to take more ownership of the whole process so I asked him what things he needed to work on. This method worked MUCH better. My little guy was able to identify his problem areas at that age (sounds like yours might be able to as well) so I would strongly encourage that method if you are able.
I also started hearing about Love and Logic around that time and it saved myself and my kids alot of grief. I haven't been to their website lately, but it is www.loveandlogic.com
I think. A quick rundown of Love and Logic is that the child is responsible for finding their own solutions to solve problems they have created. You can help with ideas if they totally draw a blank and then you ask the child about the possible outcomes of each (i.e. "well, you could throw a rock at them....what do you think will happen if you decide to do that?") Basically you just help them decide these things for themselves and they learn from the natural consequences of their actions. It also works for the tantrums or offensive behavior toward you. You let the child know what YOU are going to do as opposed to going for the immediate deman from them...."You are hurting my ears. I will listen to you when your voice sounds like mine." If they continue you hit 'em with "what did I say" (calmly) and you start to sound like a broken record, but it is extremely effective. Now all I have to do is use that phrase one time and the fuss is over with
Like I said, that was the QUICK rundown and they have so much more I can't even begin to do it justice. Hope this helps!