Current Projects chat and miscellany

First try mole grips. I bet it'll work.
Then try the slot/screwdriver technique. You dont need a dremel to do this, just a junior hacksaw
Third try the drilling, this will be the hardest for sure, especially with that non-level broken surface on the bolt to start from.

Also invest in a tap to clear out the threads in the frame before running the bolts through (it'll be built up paint that's caused it to snap). It's the same size on all frames for every braze on so chances are you'll use it quite often (I think they're M5)

If all of that doesn't work get yourself some of these puppies from Clerkenwell Screws...(tip, start with pilot hole from small drill end then work up)