As with everything else on my current project the tabs have been fighting me too. Old abused and neglected, one has started to seize due to corrosion inside the tab castings where the stainless hinge pins are and the other one did seize. I tried heat and a brass hammer and got no where. Maybe w/a real torch and a hydraulic press but w/my 2 napp gas bottles, a 1/2 hr of heat and a brass hammer I got nothing.
Was planning to try again this morning when I dreamt of the solution.
I drilled and tapped the castings for grease zerk fittings but before installing the zerks I filled those holes with penetrating oil and let it soak down and around the hinge pins. Sure enough, it broke the frozen one lose which allowed me to work it back and forth while adding penetrant. Then added the zerks and it hit them w/a grease gun. Bingo!
Finally one **** chore that worked out.

Worst case is to cut the hinge pin enough times to remove the bottom plate. It's easier to heat and beat out the smaller pieces and buy a new pin. Hope your using MAP gas not propane. Those don't look bad, Heat, pb blaster and a real hammer and they should come apart.

that if the grease fittings didn't work.

sorry for not reading it thru, that is a great idea.