Trying to remove belt drive pulley

I'm hoping the experience base here can give me some advice. Over the weekend, I was doing some PM on my 1997 10523 Gold Series 2-stroke. Since I was removing the muffler assembly to replace the drive belt and clean the ports, I intended to replace the lower crankshaft seal while the motor was on the bench. That's where I got stuck. I have an assortment of pullers, so I wasn't too worried about getting the belt pulley off, but the set screw was frozen and halted my progress. I set it up on the bench with the screw facing up and soaked it with PB Blaster overnight, then attacked it with both my cordless impact driver and a hand-hammered impact driver, all without success. The screw is so small that my bits either break off or bend without loosening the screw. It seems the only options available are to drill out the screw and re-tap the threads or use heat, except that the only torch I have available is the typical propane.
Has anyone faced this situation before? What worked for you?
Thanks in advance for any help.

Bill

Sounds very familiar. Nothing extra that I know to help. Torch heat, penetrating fluid and tapping with brass and hammer was my technique as well, ended up cutting it off with a Dremel. I ended up breaking all my screwdriver bits on that little setscrew to. Drilling the setscrew out sounds like a good plan. The threads are only in the pulley.

get that bitch red hot, need acetylene, no air.