For football - you're not going to get good shots from the stands period. Too far away and poor angle (shooting down on your subject). As Jim mentioned, your camera is not capable of high enough ISO to get night football shots. You need ISO 3200 or 6400.
And, to give you an idea, the 70-200 2.8 lens is good for about 25 yards (75 feet) of range. That isn't very much at all - certainly not from stands. Even if you're on the sidelines, it won't reach the other sideline.
Unfortunately a very important part of getting sports shots is YOUR location. So, if you want shots you'll have to get to the sidelines. If you can't get on the sidelines but have to stay outside the fence you're just not going to get many shots at night. If it were day games you could get a longer lens (like a sigma 50-500) to get you enough reach. But such a lens is useless at low light sports.