What condition are your rubber brake hoses in? Are they pinched? Sometimes that can cause issues. Can you take a hose off the caliper and get fluid through it when you press the brake pedal. I would try that one at a time to to see if you are getting good fluid flow in the brakelines. While the hoses are off you could see if the release of pressure in the caliper frees it up enough to remove it.
BTW, If you don't have them Harbor Freight has some nylon brake hose clamps that you could use to seal the line while you've got it off the caliper.
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Mike in Sydney
[This message has been edited by Mike in Sydney (edited 05-31-2020).]