@OP, I've had similar issues but don't waste your money on a name change or phial-- if this person is as terrible as you describe and really stalking you, they will just do what happened to me and look up your character via google using any of your old characters names and it will redirect him to whatever you renamed your character to/display your new race/look. If he's really paranoid, he might've just bookmarked your lodestone and then that will always keep up with any changes at all you'd do since it is done by character ID (that sucks, too, SE really needs to fix that as well as the linking old to new once someone name changes).

The only recourse left that may work, and worked for me, is transferring servers. Most people won't spend $18 just to stalk someone in a game, and if they do....well, that's a good sign it is time to take it to the real life authorities. ^_^V Good luck!!