I've spent about 2 hours taking him apart (the screws were rusted in) and trying to diagnose the problem with why he was playing at about .45x speed.
I thought it was the potentiometer at first because this thing probably hadn't been lubricated since when it was made in 1986 and I didn't feel like lubricating it all, so, just turn up the speed on the motor, right? Nope.
The motor is too old to have an external potentiometer.
So I started messing around with the (now loose) tape deck with and without tapes on it. As it turns out, the resistance from the tapes themselves was causing a rubber band to slip. So I'm replacing the rubber bands with the closest that I have on hand, I'll tell y'all's how it works out