My son has ADHD. Viola, how much have you educated yourself on the topic? There's a book for kids called "Putting on the Brakes" which I read with our son. The fact that kids with ADHD have little impulse control is a HUGE factor in what's frustrating you about your son.
I want to share with you some of my own observations which parallel what you see. Our son (10 now) was diagnosed at 7 years old. The psychologist didn't recommend meds at the time due to some anxiety tics Kiddo was having (due to being physically bullied by two other students and not keeping up at school). So, we tried discipline, went to workshops, and tried to work with the school in having reasonable expectations for our son. The thing was, our son *couldn't* do what we were asking of him. It wasn't a defiance situation, he just was spread so thin from trying to behave at school all day, the knowledge that he was disappointing his teachers, and frustrating us as his parents-- it only made him more anxious and angry with himself.
I made a huge mistake in trying to uphold the teachers' suggestions *all the time*. During his third grade year, his self-esteem just plummeted. I found out later (from other parents as well as my son) that his teacher was verbally bullying him during class due to his needing a little extra help. I regret not having pushed harder as I was trying so hard to work with her. Finally, I pulled him out to homeschool because he wasn't gaining any knowledge there, only feeling horrible about himself. It was too much pressure for an 8 year old.
It took us a year to come to point where his anxious tics had diminished. He was still having trouble with impulsiveness and focus, so we decided to try medication. It was amazing. He had the ability to *put on the brakes* and stop himself for the first time in his life. It's only been a few months since we started, and he's SO proud. We are now using melatonin (which I've been wary of for a while) for nighttime, and it's worked wonders.
All this to say, I think you are putting a lot of pressure on your son to meet some unreasonable expectations. Even typical kids don't always have the best manners. I really want to encourage you to go back to a psychiatrist and TRY AGAIN. This really is a treatable neurological issue. The haywire disconnections happening with ADHD brains can be corrected effectively. I'm concerned that you would try tea tree oil instead of trying meds again. Listen, I have anxiety disorder, and a thousand cups of chamomile tea and hours of meditation won't make me 'mellow out'... and if someone had told me that before I'd started medication for it, I'd tell you "are you high? I CAN'T." It's not a mind over matter thing, it's a REAL ability issue. The same goes for kids with ADHD.
Our son's confidence has grown by leaps and bounds. He's now focusing more easily, less distracted, but even more-- he's become far more considerate and is pleasant company for the adults and the cats in our house. (He used to be rough with them, now they trust him. HUGE!) Please, give medication another chance. Don't expect him to be a gentleman-- instead, be gentle with *him*, understand his limitations, and teach him to be kind to himself, too. Personally, I think you need to recognize that your son did a very normal thing in defending himself, in both situations. If I'd heard a kid was spraying others with bug spray, I'd expect that child be sent home as well. We, as a society, need to learn that peer correction (pushing someone doing something offensive away from us or defending ourselves) is not aberrant behavior. Telling someone to go run to adults to solve everything is problematic. I think your son probably feels he doesn't have anyone on his side. Work on that, too.