Tried applying Liquid Wrench for a few days? Ya, some might get into the line, but since you're bleeding it anyway....

Othe rnuts/bolts I'd heat them up with a torch, but brake fluid fumes are toxic, so I don't know if you want to do that. Anyone have experience trying this?

As for changing the wheel cylinder, yes you'd have to remove the whole wheel, but when the brakes are not applied, the shoes rest on the post above the wheel cylinder. If you can open one of the other bleeder screws, you may be able to squeeze the pistons in a bit to clear the shoe body. Then it's just a question of clearing the emergency brake arm. Wonder if it would swing up out of the way once the cable's un-hooked.

Of course, personally, if I were going to go to all the trouble of stripping my wheels down to the bare axles - I mean, you have to remove bearings and everything - I'd take the opportunity to do an overhaul. Spring kits are about $30, and new shoes. Add your new wheel cylinder and you have a brand new rear brake system.