He likes me but he has a girlfriend (NO JUDGING PLEASE)

Okay so first off, don't judge me please. I'm looking for actual advice, so if you can only say criticism, it's not needed. This situation sucks. Anyways, this guy and I have liked each other for years now. When we first met, we were both too nervous to tell the other, but last year, he told me he really liked me and wanted me to be his girlfriend. We are both under 18 (he just turned 16 and I am 15), and when he told me he liked me, he was 15 and I was 14. Anyways, I didn't believe in dating before one of you was able to drive (it's okay for others but the relationship would never work for me), so I told him I really liked him too but until one of of us was 16, I couldn't date him. He seemed alright with that answer, and we agreed to move on and see (or think about seeing) other people and liking them and all that until he turned 16 and then we would talk about dating again. Anyways, he got a girlfriend a little before he turned 16, and she is really nice, but really needy. He wants to break up with her and date me, but whenever he brings up the subject of breaking up, she threatens him (physical threats such as punching him), says she will kill herself and now she is even going as far to stalk him. Both of us are really creeped out, as you can probably tell, but we still want to make our relationship work. Any advice?