I'm really sensitive, too, so I can imagine how this must make you feel because my stepdad was very passive aggressive. If he thought he was successful in getting at me, it just made him act even worse because he got a charge out of making me upset.
So I think that if you can manage not to respond to this guy's comments, it may slow him down. If he continues being really snide, you might need to start keeping a log of his comments in case you have to lodge a complaint. It's really hard to prove when someone is passive agressive, though.
I hope that he doesn't have to stay in your office. :hug: