Most likely about 2 gallons.
No. Just the main tank. The warning light comes on with about a gallon left in the tank, in my experience.
Approx 2 gallons
No.
When there are 3 gallons remaining, the LOW FUEL light will come on (page 332 of pdf Owner's Manual for the 2013 model with 24.6 gallon tank)
Not that I've seen.
I am currently attempting to go 28 miles with .835 gallons of regular after driving 20 miles with the gas light on. If I don't right again I made it.
The warning light on the dash of a Dodge Charger could mean different things. It would depend on the year of the Dodge Charger for starters. There are also multiple warning lights. It is recommended to check the owners manual or have it checked my a mechanic.
By buying fog lights and installing them.
Look in your owners manual.
Look in your owners manual.
Check Tire pressure