Get a MAP gas torch, propane is weak sauce. MAP gas will heat stuff up in 1/4 the time and is far hotter.

I've made jam nuts glow red and almost to the point of melting to get them to break free with a oxy torch and MAP gas torch. While their red hot work them back and forth several spins and use PB blaster or something to break down the rust in the threads. Wire brush everything and snug them back up.