Broken Pressure Plate spring
One thing that people haven't really mentioned.
It's quite possible for the spring in the pressure plate to break (this has happened to me, many years ago on a BMW). The result is that the clutch plate isn't clamped to the flywheel. If the clutch pedal feels lighter, this may well be the problem - it certainly explains your symptoms.
All the advice you've been given is good. But I think you're going to have to pull the transmission and replace the clutch plate, pressure plate and other pieces.