Used compressed air to unstick brake caliper, only one caliper moved....
 

You can try unsticking it with the brake pedal, however if they're really that seized you may be better off with a reman caliper! You're going to have to tear that one down and rebuild it and hone the cylinders anyway.

Using brake hydraulic pressure is a lot more powerful than compressed air. The caliper doesn't appear severely corroded or otherwise not worth rebuilding. So yes, I would mount it on the car.

Push the free piston back in and insert a new brake pad on that side only. Leave the stuck piston side empty with no brake pad, or you can use a very thin worn down brake pad if you have one. The new brake pad will prevent the free piston from travelling much, and the air gap on the other side allows the stuck piston room to move. The brake rotor will prevent it from shooting out and making a mess.

I need to reinstall the bolt that goes just underneath the calipers....
 

This. :)

You may be able to get it loose, but as said above, be perpared to buy a new caliper, anyway. If it it that stuck, it is stuck due to rust between the piston and bore, which means rust pitting.