First I'd like to welcome you to the board.

As for the brake Light, couldn't be that your socket is loose or your bulbs are half burned just like mine, It went on and off all the time.

For the dash bulbs, Try to PM NhatDuongChi, he did the blue LED conversion for this 6th Gen so he should be familiar with this to help you out.

For the engine part, where's the vent valve located, I may know how to fix it, but can't visualize or know the terms.

My gas meter has the same problem, Full tank only point a lil but upper of the 3/4 meter, I got used to it.

Hopefully some1 else would help you out