Sloooow down, buddy. Let'* see if we can answer all of these for you. I've installed remote starters in many different makes so this may be a little vague for your specific vehicle
1) If you have a remote start only then yes, you only tap into the ignition wires. If it ia an alarm/remote combo then you will need to cut the starter wire (yellow) if you want the ign kill function to work. I'm not positive on the second ignition but GMs typically use a white wire the same gauge as the other "target" wires
2) Parking light wire is brown and it is +12v
3) Brake wire is white at the brake pedal switch & yes this is needed
4) Dome light wire is white wire. You can usually find this at the dimmer switch or in the kick panel. Look for the wires coming from the driver'* door
5) ??? This sounds like it would be connected to a valet switch of some sort.
6) Tach or tachless...the big debate. I prefer tach. White or violet/white at the coil pack
7)VATS wires are contained in an orange (or black) "tube" coming from the ignition. It should be very close to your other ignition wires
Try going to the door lock relay behind the glove box for the locks
9) I have a 90 SSE and my trunk release is in the glove box. Where'* yours? Connect right at the switch.
Good luck. Again this info is for typical GMs. If something is wrong or omitted, feel free to correct.