Did you try calling your credit card? I'm assuming that you did since you are saying that the charge is currently pending. I wouldn't sweat it too much in terms of them suing you if you don't buy the car from them, that would be purely ludacris on their behalf.
Just fu$$ this dealer, call your credit card, explain the whole thing and make sure they can't charge your card, and just leave it at that. Go to other dealer, the one that's closer and buy from person that you feel good buying it from. This is America and not some third world country, they can't force you to buy the car from them if you don't want to, similarly they can't just take the deposit from you.