Hi, i have just skimmed through the thread as didnt have time to read it all, but if when you pressed the clutch down the pedal sort of stayed down i.e didnt come back up all the way when releasing, and at the same time the clutch didnt engage this would indicate a master or slave cylinder issue, its usually the slave that goes first.
If the pedal came up all the way and still felt quite stiff, i.e like it was still attached to something, then again the slave could be stuck or the clutch is slipping or badly worn.
usually when a clutch itself starts to go you notice it, slipping in gears especially pulling away.
The last thing to cause a problem is the thrust bearings and holding pins, when these go they allow the clutch plate to just spin with flywheel, giving the impression that the clutch is down when in fact its just free spinning.
hope this sorta helps you.