It will be 40's-50's at game time. As long as it is dry, it will be good football weather.
It appears as though all of the walking distance hotels are booked for the night. There are plenty of 3 star hotels by the airport (Residents Inn, Clarion, Comfort Suites) that are all close to the same. Virtually anything inside the 485 belt way is going to be <$20 UBER to the airport. As mentioned before, you could even get a hotel near Carowyns or in Huntersville and the Uber will be 15-20 min tops. It much shorter then the ride I had from Miami Beach to Hard Rock last week.
The entirety of downtown Charlotte is walking distance or very short drive from the stadium. There is a Mellow Mushroom Pizza 2 blocks away on MLK (across from a park) that I eat at regularly before games. There an Irish pub "RiRa" on N. Tryon and 5th (10-15 min walk, like 6 blocks) That I like to pregame at if I'm not going to a tail gate. Many of the restaurants downtown are pricey( Charlotte Pricey, not South Beach pricey) so you may want to check them out on trip advisor before grabbing a seat.
If you end up south of the city Mac's speed shop is my favorite BBQ place in the area.