73 Duster front disc brakes dragging when hot

After much testing, head scratching (and banging), I have ordered new calipers and hoses.
My eyes and fingers tell me the pistons are in great shape. The calipers are cleaned and lubed. The sealing rings look and feel fine. Even the dust boots are serviceable.

When I pulled everything apart and cleaned it, the pistons moved smoothly although with resistance. Once fully compressed, there was plenty of room around the rotor (so the pads weren't too obviously too thick).

I adjusted the push rod between the booster and the MC, pulling it back slightly from the MC. Result: no power brakes. Adjusted it back toward the MC slightly and restored booster power, but the brakes stuck when I jammed my foot on the pedal hard a few times.

Thank you for all of your responses - so much wisdom on this forum.
I will post a follow up next week when my parts come and I can put them on.