My only suggestion to you is to stay away from her. At this point, it doesnt seem like you can accept the fact that you two are broken up and you keep getting jealous over stuff you have no control over. I think you should either find a way to cope with her being around other guys or just stay the hell away from her. Its kinda obvious that she doesnt feel the same way about you that you do for her.
As for the other guy. If he gives you any crap, ask him how sloppy seconds taste. (To put it nicely.)
