Your symptoms sound more like rubber brake hoses that have choked up inside. This is very common on old cars with old brake hoses. They look fine outside but are swollen and choked up inside. They can pass fluid under pressure so the brakes work, but will not pass fluid when the pressure is released causing the pads to drag. On your front brakes it looks like one of the two circuits is suffering from this problem but not the other. The fact that the pads release when you crack the bleed screw further supports this theory.

If the pistons in the brake calipers can be pushed back in with some sort of lever, there are no leaks, and the dust boots are intact, then your calipers are probably just fine. I'd replace all the hoses (I think there are 6 of them), flush and bleed the system, replace the pads, and go from there.