I still have the tip of the broken-off bolt with the broken-off drill bit sticking out of it with the punch permanently embedded in it just to remind me to use break-free, heat and patience with tough bolts.
Learning patience is turning out to be a very expensive lesson for me...
The bolt on the replacement caliper was hopelessly seized up too... Replacement to the replacement just ordered, this time gonna take it REALLLLLLY slowly and carefully... *sigh*