1987 Volkswagen Quantum Clutch Confusion

Transmission problem
1987 Volkswagen Quantum All Wheel Drive Manual 150000 miles

I've been driving this car for awhile now. It is quite old so it has its share of problems. I got this car from my father when I got my license a few years ago. Since I've been driving it the clutch has let out very early, almost directly after pulling off the floor. Recently it sat for awhile when the axle became disconnected from the rear differential through a broken bolt. I decided to fix it and drove it around today. I noticed it was shifting a little rough, and towards the end of the day the clutch would let out, but then stick way low after it let out, and would pop back up all the way if I tapped it with my foot. Then, while at a red light, I have my foot on the clutch all the way to the floor and the car in first. The car started idling forward as if the clutch was engaged. The car has quite a bit of torque, so this didn't kill the engine but instead almost sent me into the intersection. My first thought was low transmission fluid, but the reservoir is almost at max capacity. My next thought was the slave cylinder, but after doing a bit of research I'm confused whether it would be this or the master cylinder as I've never worked on a clutch before. What would you recommend? Should I just get a new slave or master, or should I replace the entire disc, pressure plate, etc? Thanks!