There is only one way to deal with this sort of person. Ignore them. Blocking is overrated as they'll just keep making new accounts. I've had similar problems and I've found that if you don't give them anything, they'll get bored and quit after a while. These types are extremely thick-headed and will take anything you say as a sign that you're interested in them. Whenever a message pops up from him, just minimize it and let him pratter on all he wants.

If you're afraid that he might have some idea of where you live, making a report to the police might be a good idea. Then if, God forbid, he threatens you or anything of the sort, there will be a lot more the police can do.