Take a nut smaller than the head of the bolt & weld the inside of the nut to the head of the bolt. You should have plenty of room to place a thin walled deep socket on the nut you just welded on and spin that baby right off... Piece of cake!
Yup, you're screwed! Timing belt is toast... Just a guess but it sounds like your b/s belt broke & got caught up in your timing belt causing it to bind up & break or ground all the teeth off the belt. Might just as well remove the timing belt cover to take a peek at what happened. Either way it...