Good news, everyone!
So enough was enough, 2 months later I finally decided to do something about this, and I finally got the glove box open! I think I just pulled down on the damned thing, and it just opened up; it all happened so quick that I really didn't have time to process what just happened lmao. My nose got a light tap in the process, but who cares!
Anyways, I'm really happy about this because I finally got my heater to work! All that happened was the loop from the end of the cable came off the mechanism that changes the temperature, and all I did was just slip it back on! It actually works perfectly going back and forth, but I'm not even going to touch it again until the warm weather is here, since it's a near 30 year old truck, and I don't trust it to hold lol
Anyways, the engine is cold and it's already blowing warm air; I can now finally fully enjoy driving in the winter now!
I bought a thermostat thinking that was the problem, but I'm really not too broken up over buying it since the engine temperature only goes a quarter of the way, so it needs to be done regardless.