Amon_Devilman:
I think its best for you just to go your own way and lets things die.
Your situation sounds way too familiar. Except my friend is the female. She pretty much has dealt with it and moved on.
But the guy used to badmouth her a lot. And tell people off her and her friends. I experienced that first hand. But one of the people was and is still my friend so I eventually met the others. And believe me, they are not bad people like the guy tried to make them sound like.
You must understand that from the other side, things seem and are just as bad.
You can't let things like this affect your life. So what if you have to deal with people you've had problems with. Being around and dealing with an ex may be hard but you just can't let these things carry on after many years have past. Just do your own thing and if you run into said party, just ignore them. The drama will die down if you just leave it alone to do so. Even though you may be writing things to get advice or just to get stress out, remember that it can get back to the other party involved. Even if things have died down on the other end, such things can incite more drama.
Also, just know that friends of the other party are not always acting in behalf of said other party. They may just want things to work out and drama to die away. You may or may not be the same guy as the one I dealt with before. However if you are, I ask you to just leave her alone. She does her own thing and is happy.