Advice, please?

Take him back, but this time, be really clingy, bratty and everything he hates. That should make him back off.

... do the only sensible thing....

перфоратор, удар, пунш him in the face and run >,...,<

Hm sorry for asking this but why do Ты hate him Ты should at least give him a chance:)

Ahhhhh the old 'i Любовь Ты I Любовь Ты not' I've sort of been there just tell him Ты hate him and that Ты really mean it don't threat или anything but yeah tell him that Ты two are just not meant to be togather and that Ты don't wanna ever be togather with him ever again and if he still comes at Ты say something similar to what Ты did but make sure Ты say it in a calm serious firm tonewhere if Ты just yell at him he'll just think your joking или something

Well, obviously, this guy is a biscuit. To deal with biscuits, Ты need to just ignore the living crap outta him. he will leave Ты alone.

Tell him that you'll never get back together with him. If he asks why,tell him that Ты don't want a boy who cheats on Ты and calls Ты a slut. Get him out of your life.

Tell him that Ты hate him and if he doesn't leave Ты alone you'll drop a heavy metal Пианино on his head.