OMG, that's a terrible story.
You know, I once did a mistake and lost all my friends because of that (at least nearly). It was around Christmas, I was upset, I was desperate and so on.
I tried to reestablish myself, but it was not worth it. Then I just accepted that I have no chance anymore in this group. Then I found new friends and am happier than ever in that group, although all are from outside school so that it is quite tough at school, but I just don't care aobut that anymore and when the day is over I see my "other" life.
In your friend's case, I think it is a bit similair. You call him your friend, but on the other hand you say that he is getting on your nerves. You said your group doesn't like him any longer, but I ask myself if he ever wasi n the group then. I mean you said he is not a real memeber of it. Probably he has to recognize that first of all.
The thing about killing himself: He sounds desperate, but also afraid from death. This is only a way to catch attention, but nowhere at all a serious intention he has. He wants to be tolerated, accepted, but he sees that he fails all the time, so now he tries it that way.
I really don't think that he will kill himself. You should make him clear how you see your friendship, the future for him in your group. Maybe you should propose him not to do anything together for a certain time span and when he feels better he can come to you and have a talk about everything.
Hope I could help you a bit.