wow-
why do people go for death when all it take is patience and/or the right tool.

OK the cap was shot, a modern heatgun will do wonders

penatrating oil and time

tapping on the cap to try to crack the corrosion

using dremel to cut a slot thu the threadwall of the cap and then getting it out

if the threads were usable..

heatgun the arm for 5 minutes and try the puller.

if the threads are shot- the arm is gone-destroy arm and salvage axle

drill a series of holes across the crank arm use a chisel to crack it

you would have saved the axle..

heatgun is a must for a bikeshop!