I work on heavy equiptment, and have run into stubborn nuts and bolts
many many times. and I have found that the only, and simplest answer is
heat. You can sit and hammer, chisel, bang, beat, twist,squirt,or
whatever else you can think of, short of TNT, when all you would have to
do is heat up that little lug nut cherry red, put a vice grips on it,
and lo and behold its off!    Been there,seen, it done it.
Good luck
Terry
85 GL