Broke my water pump bolt. Now what? (Update - broken bolt is out)

That propane coffee warmer will be useless. Need at least a bottle of mapp to get it hot enough to make a dent if not an oxyacetylene setup.
Another thing I've had work is a "bolt buster" type inductive heater to get that stub cherry red before you try the vise grips
i agree on the "weld a nut" being the best shot.
Be careful with the hammer trick, if you don't hit it dead square, you might well crack the ear off the block