slinkstar, I feel for you, I really do. Your situation almost mirrors my own.
My DS1 (10) has violent periods, then calm periods, no pattern.
The thing that I really struggle with is my feelings towards him when he's like this. After years and years of this behaviour it becomes overwhelmingly grinding, to the point that I almost feel emotionally switched off. Horrible feeling.
Like yourself, you dish out the punishment to fit the crime, hitting is worse than teasing, therefore, the hitter should receive the harsher punishment. I think other posters are probably right that we should maybe work more on the 'teasers', my DS2 (8) is the teaser, albeit mild, but he is SUCH a good boy, and he is heart broken when he is told off, I just couldn't face punishing him, if he's ended up punched or pushed as a result of the 10 yr olds anger. What I normally do, is take DS2 to one side afterwards and explain that DS1 has difficulty controlling his anger, and that the violent incident was a result of his teasing etc.
I'm still working on it.
Sorry if my post has gone on a bit. I would add that I sought help for DS1 a few years ago, and they've said he is somewhat of a conundrum, but they think he might have mild aspergers syndome. He's fortunate that his school provide anger management lessons. Is this something you could maybe ask your school about?