Re: back light
It is possible to force the bulb in the wrong way round and it looks like that is what's happening, if you look at the position of the locating pins on the side of a 5w/21w tail/brake light bulb you'll see that they're staggered.
If it's in wrong that side will have a 5w brake lamp and a 21w tail lamp which means when you operate the brakes at night it's working but the tail light is brighter than the brake light. Have a good look at the bulb and bulb holder and you'll see what I mean.
You may already know this so just ignore me wittering on if you do.