To put a good spin on the problem, you have the ability to work on both ends of this screw. It’s been a few years since I’ve worked on one of these, but I think that’s a fine thread screw. Probably 1/4-28.
Lots of penetrating oil, heat, and patience should be the key. If you drill from the bottom, a right hand drill will spin in the direction to loosen the screw on the head end.
Improvise-Adapt-Overcome
