Brake light switch and rear lights help

Pretty sure it's high up by the top of the brake pedal lever, and easiest to get to laying on your back.
As far as the lights go: you can check for needing a better ground, you can just take the lens off and clip a ground wire to the car.
Use the other end of the wire and touch the bulb base where it goes into the socket.
If the light gets brighter it needs the ground circuit tended to.

About the brightness these lights suck stock, and I went to LED's on mine because of that.
Depending on a which angle if any your bulbs are positioned in thier housings you can get some nice LED's pretty cheap on Ebay.
Search 1157 replacement LED on ebay and check it out.