Sorry bro but pulling a knife is a bitch move. If you can't win a fight without pulling a weapon your a bitch imo.(not saying your a bitch, i just dont like knife fights) OP, i'd honestly just meet with him, be polite but firm in telling him that if he doesn't stop this bullshit soon your going to come down on his ass. Dont just run up and hit him like a spaz tho, talk to him first. If you can, intimidate him enough that you wont have to fight him.
the problem is the start of this sentence. Dating a high school girl is practically asking for the drama, even if the age difference is small.
yeah I know, but I'd deal with it all for her, i may not like the drama...but hell least she's graduating this year Also sounds like saying something to the kid first might do some good, I usually try speaking with someone before choosing and a more violent means to and end. Even if the kid deserves an ass whoopin if I can end this without fighting I might as well try. But I don't hold high hopes for the talking method
I wouldn't fight him. Then your just descending to the level of high school drama that you are trying to escape. IMO, of course. If it were me, I would calmly talk to him about how it is not alright to do that. If that doesn't work, I would threaten the whole sexual harassment thing, and the consequences of it. I don't recommend actually pressing charges, but I think threats like that are better than an assault charge.