electronic or wiring issue?

I have a 2003 Chevrolet S10 ZR2 with the 4.3L Vortex engine. I recently purchased it with known electrical issues. When I bought it the radio was gone, the a/c temperture adjustment knob in the center did not adjust the temperture though the fan speed selector knob and the air directional for vent defrost etc worked. All gauges and instrument cluster lights work and even dim with the selector switch by the headlights. All headlights blinkers horn wipers work. The pwr windows do but the door locks and the pwr mirrors do not. The 4wd selector does not light up or work. The interior lights and lights on the mirror do not work as well.  There is a security light that blinks on and off when not started and the red air bag light is on. The passenger side has a on off switch for the air bag that you use your key and it works. I bought it thinking ground issue but since purchasing it I have cleaned the negative cable going to battery. cleaned the radiator core support ground. It was dirty and loose. Cleaned the large braided line that goes from the back side of the engine to the firewall. It was real dirty and very loose. Cleaned 2 ground locations under the dash on the firewall next to the steering column. One was rusted and had a ground wire that had the insulation melted off of it. I followed it back and found good wire and replaced it. Still nothing. So I decided to just reground the devices that did not work I thought I would do a test run on the interior light first. So I took a known ground that I had installed and installed it to the interior light. Now the light does come on. But it will not go off now withe the doors closed and selector switch in the off position. I also thought it might back feed some of the other devices if they all went to a common grounding location. The only other thing that worked is the light in the ashtray.  Does anyone have any ideas as to what I should try next? I am wondering electronics but all along I have been thinking hard wire issue. Is the temperture selector switch from heat to cool a potentiometer stle device or how does it work. Should ground be an issue with this?

-------------
I like to pick up where the factory quit.

The first thing would be to disconnect the battery for about 20 minutes then reconnect, see if that cures anything.
Diagnostic equipment an absolute must with this range of problems.
Physically with a meter check ALL the fuses.
Also sounds like body control unit problems especially related to mirrors, locks and dome lighting.

-------------
Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.