1. So i got myself a blackbox dvr/dashcam. Now i want to rid of the cigarette lighter plug and hide the wire in the headliner DIY style. Where do i tap to get a live 12v connection from the stock wires of the car?

2. Then i got some light accessories which also needs 12v of power. I want to install it in a way that when i open a door, it would light up/function. Like how the stock dome lights behave. Where do i?

3. Now if i need another 12v source for another accessory, can i go ahead and tap it in addition to #1? If no, where else can i connect to in the stock car wires?

I got the fuselage and switch covered.

P.S. Will #18 automotive wire do? Or should it be #16?