Originally Posted by
frand 
My question is: at what point is it okay to simply cut all contact?
You'll know when it's ok. It's when you've had enough, when it doesn't matter what other people think, it's when it's the right time for you.
My brother is my A too, I'd have cut all contact a while ago but I have his son living with me so it isn't so easy. He lives about 200 yards from me but I choose not to see him or have anything to do with him other than when I need to because of things regarding my nephew. It works for me.