Car stereo install help

You will not be able to connect any of those controls to the replacement unit. They are designed only for the OEM system and use the cars computer network to control the factory stereo through the body control module.
What most places do these days if they can, is to remove the OEM stereo unit, extend the factory wiring harness and tuck the OEM stereo out of the way under the dash or seat. Then you connect up a single front speaker to hear the chimes and warnings.

The new unit gets connected in as a stand alone stereo. Using a relay for the switched power and a direct battery feed. They might use the factory speaker wiring but only if the vehicle does not use any remote amplifiers.

Your battery draw is probably because the OEM radio does not fully shut down so the power to it does not shut off. This is again because of the data bus that controls the vehicle. You will probably need to find different non computer controlled power for the unit. Dimming through the factory system likely is not possible because it is not a simple low/high voltage, it is a PWM modulated signal using a five volt reference that tells the chip in the OEM radio how bright it needs to be.

The old days of just wiring in a stereo are long gone because in most vehicles the radio is not just a radio, it controls much more and even stores data from the vehicle. Most are also tied into the anti-theft system.

Good luck.

Battery for full time power, there should be an orange lead for direct battery power. There is a second orange that is a computer data line. Just use a meter or test light to determine which orange is the battery feed.

For switched power you will need to find the accessory relay in the console fuse block and use it to switch another relay that you connect to battery power. That is the only switched feed that is not computer controlled.