well from your post it seem pretty clear that there is not much about this guy that you find attractive to continue corresponding with him. i think you hit the nail on the head with your bpd making it hard to let go. without friends or other prospects you will be alone and who wants that? so ask yourself if the frustration of dealing with him going to make you feel worse than the idea of being alone and seeking new friendships. the healthier choice is to let him go. but it is really up to you.