get a shoe lace and tie your foot to the clutch pedal. Instead of releasing the clutch yank your foot up faster than the pedal can normaly raise. It really does sound like your clutch is just, well old and worn.
Describe the slack a little better, are you saying there is an inch of play before the clutch engages, or that fully engaging the clutch takes an inch of movement. Also explain exactly what happens when you pop the clutch, does it engage?