My full sympathies to you my friend I had something very similar happen to me back in the early nineties,this guy would not leave my girlfriend alone, she had a young son off this guy before we met, well basically he looked at her as his property, he said if I didn't finish with her he was going to kill me! So I arranged a meet with him, I asked him this do you love her he replied no just want you two finished, I said ok then I'm not finishing with her? He then walked away, then the fun started vitriolic accusations about me threats abuse even to the extent of him smashing me over the head with an house brick breaking my skull, still I would not finish with her! Then the bombshell she decides to finish with me to run off with her best friends husband ha? So ok i except that even though by this time we have a daughter, i had started to realise my focus was more of not giving in to the intimidation, i was not in love with her anymore! The whole scenario finished when I decided to give one if his mates a good hiding, then one of my mates going in this guys local and offering him out, the problem stopped overnight, the same guy now is doing life for a murder in London, the guy has been in years. The only advice I can give you is do not give in to his intimidation, he will carry it on even if you finish, he will want you react so he can say I told you what he is like or get the police on you, you have to be more clever, if the police won't or can't help you, intimidate him back but be very clever, get people to threaten him make his life uncomfortable, tit for tat rumours are no good to this guy he will brush them off,but try to do it above the law, looking at your problem I can see this coming to an head very shortly, make sure you have witnesses to your every move? It will stop eventually, but give him no quater.