Please don't be so hard on yourself. You are searching for answers, which means you haven't given up on him! And don't!!
Have you tried to talk to the parents of the other boys involved? Maybe they are going through the same internal turmoil as you are.
If it were me, I would not be so quick to jump into counseling. Sometimes I wonder if that does more harm than good, as the child then feels "labeled" or that there is "something wrong with me." JMO.
My advice is to just keep on him. Keep hammering it into his head what is good behavior and what is bad, what is acceptable and what is not. Come up with a discipline plan together. If you do that, then this is your punishment. Once you have it in place, stick to it. Don't let him see that you are going to back down. Hold up your end of the deal, so he sees that you mean business. And most importantly, just keep loving him, no matter what he does, although some of that love might need to be tough love. This might get worse before it gets better (I hope for your sake that it doesn't), but just remember if you need a sounding board, we are here. Good luck to you all.