I'll say it again, if you feed, you will revert back to a mostly normal form that will allow you to speak to people. You're stuck in the Mages Guild, right? That's perfect. Just wait for the night and drink from everyone in there.
For the cure, you can simply ask Raminus Polus at the Mages Guild about it. He will direct you to the count of Skingrad, who will ask you to do a quest for him. You can get the cure after. No need to be in the DB.
~Dark Cupcake of the Sith