I would disconnect the brake line and drain it and move it away from the backing plate. Disassemble the wheel cylinder as much as possible and clean as much brake fluid out as you can. Heat the wheel cylinder from the front side, near the bolt bosses, try the bolts to see if they can be moved.
1957 Chevrolet 5700 LCF 283 SM420 2 speed rear, 1955 IH 300U T/A, 1978 Corvette 350 auto, 1978 Yamaha DT175, 1999 Harley Davidson Softail Fat Boy
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