[Sirc]

^ from memory I don't think the frame is tapped but I could be wrong - i think there is a tapped (loose) collar instead. You will get there in the end with perseverance - it helps to move the bike next to a sturdy wall and then arrange wood etc to brace between the frame at point of impact and the wall. If you feel like waving the white flag on removing bolt conventionally then as a last resort you can carefully spread the frame enough to get a pad saw/junior hacksaw between the crankcase and the frame to cut through the offending bolt.