mirror auto dimming is normally controlled by the sensor in the rear view mirror. (when light shines thru the rear window the sensor detects it and dims the rearview mirror and drivers side mirror) the sensor on the backside of the mirror (facing forward) also detects ambient light and dims the interior lighting, cluster, radio.
do you have the stock radio or is it aftermarket? and if it is stock does everything work? I believe the stock amp operation communication is thru the radio so if it is aftermarket that might explain why you are unable to communicate with the amp or perhaps you are selecting the wrong radio or amp with the tech2?
headlights I have pretty much always ran HID or other aftermarket lights and have just ran the ground from the headlight harness right to the frame. (leaving anything else intact)