How can I stop being jealous?

If you want to stop being jealous you could be happy that he's found someone that makes him happy.

If you want to break him up, it will probably just backfire anyway because it's not like guys are totally oblivious to the manipulative bs girls pull on us, he'll figure it out and then never go out with you. When a girl you know is trying to get in between the girl you're with, it's always really obvious and it's always made me hate the girl for being messed up and trying to control my life for her own reasons.

Far as your friends go, that's pretty much how guy friends work. Guys don't usually keep a friend that's a girl that they wouldn't screw given the chance. It's not like every guy constantly wants to do every girl he keeps around, it's something more like we just accept not doing them.

If your guy friends are constantly trying to get with you or do romantic shit that you don't welcome, the best way to stop that is just tell them you like them as a friend, but if they keep trying to push it to something more, then they won't even have your friendship much longer. Guys will sometimes be a girl's friend so that they can have a chance for boyfriend status later, and that's probably what most of your guy friends are doing. Keep in mind they might genuinely be ok with just being your friend, they'll just get hopeful from time to time.

Last thing I gotta say is you sound like a bad person. In your question you mention how bad looking everyone is right after you talk about them, you joke about breaking up someone's relationship, you put two totally different questions into one for no apparant reason, and your question title asks about how to stop being jealous as if you've never heard of being happy for someone else's good luck in life. I might be a bit biased, cause I'm a good looking guy who from time to time likes to go out with nice girls below my league, because even nice ugly girls are nice girls and it feels good to give em a break. It's the girls who judge guys based on how good looking their girlfriends are that makes me have to second guess my charity sometimes, and it's a lot more annoying than your selfish little problems.

The special needs guy, if its to the point of frightening, stay away. You can never know what handicapped people are capable of and getting physically hurt, that wouldn't be good for either party. For the rest of your guy friends, somehow you have to let them know that their in the friend zone.
hell you could could help them to improve their looks so they get other dates, if they get the hint that your helping them find other women, they'll start to notice other women.

-he must not think she's ugly if he's dating her. You should just forget about him, instead of trying to break them up. 1) you should be glad he's happy with her, even if it's not with you and (2) that would mean that the guy you like is fickle and flighty if you did succeed in breaking them up. If you got him that way, that's how he'll leave you.

-just let your guy friends know you only like them as friends. And stay away from the special needs guy.

First, if you really like this guy and you wanna go out with him, I'd break them up. Maybe that's just my personality but I don't know. Just make sure he doesn't know that your doing it. But if you just want to forget about him just find another guy that you like.

second, if your friends like you and you don't like them like that, just say that you don't see them more than anything but a friend. There guys they won't really care, because in the next day or two they'd probably be after some other girl.

third, stay away from the special needs kid. You do not know what he's capable of and yeah if he scares you just stay away.