Sounds lime aminimum of 3 unrelated problems.

The problems with the door locks, trunk, and gas door not opening, as well as the flickering light on the dash, that all sounds like possibly the "pump" under the rear seat, called the PSE, is bad. Fairly common. Is it possible this is a flood damaged car? The PSE is in kind of a low spot in the floor pan of the car, and is in primo territory to get affected by a flood or deep water.
Check the foam cover around the PSE, as well as the rear fuse box, for dampness and/or corrosion.

The AC/blower fan wouldn't be vacuum related. More than likely the blower regulator or the fan, or both. Again, very sensitive to water, and I've seen these fail due to flood damage or a plugged plenum drain.

The transmission, maybe flood damage to either the trans control unit OR a part in the shifter called the range recognition switch. The range recognition switch is sensitive even to cleaners sprayed onto the center console, or spilled coffee or soda, so a flood could also damage it. Could be a internal transmission problem also, of course.

It just really "smells" like a flood car.

Gilly