been watching your thread with interest.
Maybe i missed it, but why can't you simply unbolt the cylinders and use some careful "wood-cushioned" hits with a mallet to either pull the cylinders from the pistons or get the crank to move or both?
I admire your patience. I couldn't wait this long.
+1 on the heatgun advice unless you're very experienced with a propane torch. leave the pistons, focus on the cylinders.