Surely the bolts are the strongest part as you don't want them snapping and the wheel falling off, and if they have snapped, what has that done to the threads in the hubs? it must have stretched them
Individually the bolts don't need to be the strongest part as there are 5 bolts sharing the load.
I agree with the above, never use an airgun to tighten up wheel bolts, for the sole reason that if you have a flat you won't be able to get them off at the roadside. Of course this doesn't apply if you're the best mechanic in the world
To the original point, weld another bolt to the thread of the snapped one and then loosen via the welded bolt. Much easier than removing calipers etc
Good luck buddy