I am sorry to see you leave, StarryStarry. And I am very sad to see you in pain. It must hurt loads to have someone who causes you so much pain around, and then be asked to PROVE this pain, too. Not being believed is terrible. Yet you are standing up for your needs, first by asking for help and then by planning to leave, this is the good bit, I am glad you can do this!
Could you maybe also take a step back and make sure the pain is not making your life even harder as it drives you into rushed decisions? You are already dealing with loads and here I am asking you for more, but if you can, it might help you. You say Rain said "she was going to contact this person and talk to him". Maybe a mod telling him to leave you well alone would accomplish this. After all, he would probably be kicked out if he failed to comply. Would this help you? You could ignore him, and he would have to ignore you. And nobody needs to prove anything.
Whichever decision you make, do know people here like you.