I have 2011 LE. When my light comes on and i fill up immediately i put about 14.2 gal into it. So i'm gonna say that it's roughly 4-4.5 gallons left in the tank. As far as how for can you go when your light comes on.... Well do the math. how many miles to the gallon are you getting. It's hard to anyone on these forums to tell you. They may be getting 33mpg because they are highway drivers and you may be getting 20 miles cuz you are all stop and go driving... You have to know your own car and know how you drive.
I have gone 100 miles on the light before, but that was highway. and i didn't want to push it too far. and that was an emergency.
But as stated by previous person.... why would you want to push it and suck up all the crap in the gas tank?