Dude, you seriously need to just get as box made for your car and that woofer, take the car in and have the wiring checked out, and then come back. Nobody can help you until you have a box without all sorts of holes in it (besides the slot) and a HU that is wired properly.
On my 960 I can adjust my bass from -22 up to +6, and it stays between -12 and -20. If you set your gains with a meter you won't need to crank them to the +, it just distorts your woofers.
Lastly, you remind me of me when I was 6 yrs. old as far as your construction goes.