Last ditch effort -- remove the slave rod and fasten a ratchet strap to the rear frame area of the car and the front of the strap to the end of the clutch fork. See if you can normally disengage the clutch by ratcheting the strap tight. If that fails, then you must pull the bell housing off and look inside to see wtf is going on. Who knows, it could be something really bizarre like a bolt from the factory that is stuck inside the pressure plate somehow. But if you can't disengage the clutch manually, by eliminating the entire slave/hydraulics/master/pedal assembly side of the equation, then the problem is inside the bell housing.
