Van pulls to the left when braking?

My van pulls to the left when I brake. Okay, when driving straight ahead. Right caliper very hot after driving (slow speed, straight ahead) for 10-15 minutes.

I believe that the piston on the right caliper is stuck in the brake-applied position. I tried to remove the caliper per the Dodge service manual:
- remove upper and lower retainer clips and screws;
- There are 2 Keys that hold the caliper in place. Dodge calls them "Adaptors". I tried to remove upper and lower Keys (they are supposed to slide in and out), but I cannot do it, even after tapping with a steel rod and hammer.
- Result: I cannot remove the caliper since the Keys/Adaptors (K/A) cannot be removed.

What caused the K/A to be stuck in place so hard? In my Ford Ranger, the K/A slides off easily when tapped.

Thank you.

Henry