Better watch it with heat, hammer, and chisel. That's a dangerous combination. I had one that was hung up like you are describing. Over a period of about 2 weeks, I went out daily, sprayed both sides of the pedal/rod with Kroil, and worked it up and down as best I could. After two weeks, it freed up and was fine. Never had another problem with it. Since you've already heated the pedal, this may not work at all. Heat does some funny things to metals. Some metals expand and stay. Some metals expand and contract. Some just get soft and others get brittle. It all has to do with the kind of alloy they made the part from. I think I would disconnect the brake rod, and turn the pedal as much as you can, repeatedly back and forth, and see what happens. If it's REALLY hung up bad, you're likely going to tear it up getting it off the tractor, so you might start looking for a replacement.
1951 Farmall Cub, Cub Cadets 102, 104, 1811, 1864, Simplicity Legacy XL 4x4 Diesel with FEL, 60" mower, 50" Tiller