Hi Lil, and welcome to the Shack.
Firstly, 16 gauge wire should be fine for the rears. Thin, but will do the job (and can be upgraded later). The fronts are usually best with 12awg or greater, but you won't notice anything unless you have good quality speakers.
The rear speakers are fine at 6ft off the ground, but the fronts (all three of them) should be level with your ears when you're sitting down.
Lastly, I think there might be something wrong with your shift key...
