Hey congratulations on diving in on this. You are doing great.
Question 1. They aren't designed to come on with the headlights. You'd have to modify your circuit.
Question 2. Do you have a turn signal switch that uses the brake lights?
It is correct that either terminal of the brake light switch is OK. And it is correct to have it on the light switch for power at all times. The other wire will run either to your turn signal switch or directly to the light assemblies.
#3, there's a chart somewhere on the internet. I forgot where I found it.
#4, Need to ask supplier.
#5, that needs to be checked with a meter.
