I've unthreaded some stubborn knobs by wrapping with course grit emery cloth and then using a small pipe wrench to unthread the knob after soaking with Kroil penetrant for a few days. Usually works for me. Paul J.
Glad to hear you got that shift knob off. Maybe someone had used Loctite on those threads in the past to keep it tight. It seems like the shift knobs on my cars are constantly coming loose .