Who on here did you get this dog from?!?
I'm suprised he/she won't take the dog back and return at least part of your money. Dogs that are known to have certain aggression issues can't be expected to go to a new home and not possibly be returned. You two never discussed that potential aspect of this transaction?
You could've found a low cost to no cost Yorkie and been better off it sounds like.
Best of luck to you all. If you were in Illinois, I'd offer to stop by!