If it won`t come off with heat then I think I might cut down into one side of the nut
with a cutoff saw. I`d keep heating it up and spraying PB blaster or WD -40 while HOT. I`ve not noticed much of a difference
in the two lubricants used this way. Get a chisel and get a good bite on the edge of the square angle of the nut and give a good hit.
