Congrats & welcome!
Sounds like you found a good one with those low miles.
1. Its probably the key has lost its charge and needs to be charged and re-programmed. (charges in the ignition)
or , how close to the car are you? they don't have much range.
There are several programming options for unlocking, sounds like yours is 2 pulse to open all. (with key)
2. i haven't seen a quick fix for that one
3. I'm sure there are, someone may chime in with recommendation. (not a fan myself)
4. Eisenmann is one of the more expensive aftermarket exhausts, they sound great.
5. needles dont light up that Im aware of. (had to think about this one, dont drive much at night)