I'm sorry to hear what you're going through op, but generally cutting some one out of your life is the only way to deal with things like this. Its a bit harsh, but you'll both be happier for it. Just deny every avenue he has to contact you. Have your friends /blist him, ignore him when given the option and never respond. Even posting this on the forums is enough to goad him on because you're giving him an indication that hes bothering you. Eventually, he'll grow bored and find some other poor soul to torment.

Just picture him as a bad memory, and soon enough he'll become one. Eventually you'll forget he ever existed.