The remaining front brake tasks were to replace the brake hose and bleeder screw. It took a bit of muscle power (not mine, but Chris') to remove the brake hoses and replace with new ones, but this was quickly done. The first bleeder screw went similarly and all that was left was the other bleeder screw.
The first idea was to notch a slot in the top so that flathead screwdriver could be used to unscrew the bleeder screw out. After overnight soaks of B'laster, I tried to unscrew the bleeder screw with a screwdriver but the metal was so soft that the screwdriver just peeled the screw notch apart.
The second solution was to drill out the bleeder screw. We drilled out what I thought would be safe enough without drilling into the caliper itself, but the metal seems to be solidly fused to the caliper.
And so...after all this work - the cleaning of brake calipers, painting brake calipers, buying new pistons and going through the difficulties of brake assembly, I'm looking at buying new calipers.