Have you disconnected the inside linkage and determined that this shaft is the only thing frozen?
You would think that with the pedal welded to this shaft that it needs to be released from the inside to get it out. Looks kind of bad, may have needed more time with the snake oil to loosen this up. I will admit sometimes I don't have much patience either. The pedals will stick if not used and lubed as mentioned in prior post.
Your tractor has lots of mechanical linkage, good cleaning and lube up the rest of them to prevent further problems, I recommend a small squirt can with light oil to keep them in shape.