My male friend won't stop flirting with me. I dislike it.How can I do damage control fast AND get him to stop?

A boy I'll call Jet* flirts with me when I'm already in a relationship with a boy I'll call Ilia*. I wear a ring as a status symbol. Jet* always does it and it's really annoying. I told Ilia* and he was pissed. Jet* always tries to take my ring off my finger and always says stuff like, "What Ilia* doesn't know won't hurt him" and "God, you're hot. I bet Ilia* doesn't tell you that". Jet* sometimes stares at me. When I tell him to stop the behaviors listed above and that what he does borders on harassment, he always says stuff like, "Shut it, sister. Quit ruining my satisfaction for me" or whistles at me. I tell Ilia* and he says stuff like, "What he's doing doesn't just border on harassment, but it IS harassment". I wear a ring to show Jet* I'm in a relationship, but he ALWAYS tries to take it off of my finger. When he hangs out with a boy I'll call Adam*, he always says, "Shh" and tries to touch my glutes. When he does this, a boy I'll call Michael* tells him to stop before he gets in serious trouble from Adam*'s,Ilia*'s, and my parents. Adam* always calls him a moron and tels him to stop his moronic antics before Ilia* and I get REALLY PISSED and it ends ugly for Jet*. Again, he tells Adam* to shut up and to "stop ruining his satisfaction for him". Ilia* always hangs around Adam*, Michael*, and I before class and we talk the situation out. Ilia* always says things like, "First he's making sexist comments about her and NOW he's flirting with her. That doesn't make ANY sense" and "Where I'm from, that is NOT how you treat a woman. Call me out if I'm wrong, but that is NOT how you treat a girl. Loves you or hates you, that is NOT how you treat a woman. Call me out if I'm wrong". Adam* and Michael* ALWAYS agree with Ilia*. I dislike how Jet* treats me and it also affects Ilia*, Michael*, and Adam*. I never did anything to Jet*. It's gotten to the point where I feel unsafe at school. How can I do damage control on the situation FAST, as well as get him to stop doing what he's doing? I'm really scared.