One thing that might help. This is kinda stupid, and it will be hard. It serves 2 purposes though. If he were to say to you, "I'm going to kick your ass," you could turn and look at him and repeat it LOUDLY. One thing, it should embarrass him, and two, it should get the teacher's attention. If you get sent to the office, oh well. It gets you out of harm's way and might get the ball rolling. You could also say back, "What, what's that, you're going to KISS my ass?" If he calls you fat, go to yo mama jokes online and find a good comeback. (you're mama's so fat, she stepped in front of the TV and I missed 3 episodes).
I taught my first child in progression: A girl was bullying him in line at nursery school. I told him to "ask her to please stop." That didn't work. I told him to tell the teacher. That didn't work. Then I finally had to tell him to do it back. You hate to resort to it, but you may have to.
Just keep talking Kim. We're all here caring. And you only have 5 months left, and you'll be free of them forever. Then you'll go on to make yourself something much more than they'll ever be, and when you walk back with your chin up to your reunion, they'll drool
and you'll know better.