Ive had that kinda luck hell i still dont have my New Engine and Turbo running properly in my 780 so i understand your fustrations, this being a water pump bolts should be an easy removal job with an Easy Out, drill a hole in the cetner of the broken bolt grab and easy out and remove, get a Tap if needed and retap the hole, wont be needed if drilling is done with car, get new bolt and reinstall, save your self more headache and get new bolts, ive resolved to the fact that i push to hard on wrenches and just replace bolts when reinstalling.

Remember she is OLD with lots of mileage under her belt, ive had some volvo's that were as reliable as my 03 corolla and some that were big pieces of shit like my wifes 03 V70, sometimes its better to set her afire and get another. :)