get my teeth straightened (they needed it, not just for looks but for health issues) and that it was the same as getting a boob job. Was he jealous or what? or is he just a headcase

Forget him and ignore his violent words! It sounds as though he is angry that he is not your boyfriend when your looks have improved! He dosen't want any other guy to have you so he is trying to lower your self-esteem. I would just tell the nutter where to go!! Hope this sort of helps x