Sorry for being late to this thread guys. I've been extremely busy getting the boy ready to play 16u baseball for Team USA this weekend in Canada, so I have not had time to be online as much. I agree with all the advice JUSTA6 has given you.
Let's talk about why you are not getting any air out of your air vents. Do you get any air when you set it to Max, Normal, Vent, Heater, or Bi-Level? If you are not getting anything at all, then I suspect the issue is the flabber door cable is disconnected. The slide bar you move is connected to a cable that opens/adjusts a directional door that directs the air to either the windshield (defroster), air vents, or to the driver/passenger feet. I suspect that this cable is disconnected from the door and it is stuck point towards defrost. The door is located under the dash on the passenger side. You will have to remove the A/C ducts to get to it.
Your car has a T-connection to the engine fan for a reason. One is tied to the engine temp sensor, so the computer will turn the fan on when it reaches its operating temperature. The other is when A/C comes on. A/C adds heat to the engine and therefore when A/C is switched on, the fan comes on to allow it to cool the engine. Some Firebirds had dual fans.
After reading this thread, are you stil having a problem with the interior fan when you turn it on, does it still shut off on the first and last setting like it does in your video? Or is it fixed?