you mentioned the answer
football yes i used to play football too when i was in school and before that too, its damn awesome cardio game if the ground is way bigger lol
well if you are already doing this much cardio and not doing anyother workout or not a member of any gym , and hmmmmm according to your age n height i think 65-70 will be fine i think , so what you have to do is if you became 79 from too much fat body then i'd say to lose more you should now focus on diet , in bodybuilding.com you can find many plans about diet , and about abs this part is really hard trust me doesnt matter how much good you are on your workouts with , if your intake isnt right you cant make them reveal , and i'd say play football as much as you can but you cant record that how much you run n stuff
so running is a good alternative you can also use jumping and make it harder as per your goal, but again take care of diet bcz you may get 68-69 after alot of running and whole body workout( if you want to)
and another suggestion is if you follow a plan of whole body workouts it'd be helpfull too to lose fats , bcz playing a game in irregular manner with more time and doing workouts in a regular manner with less times have differences so save your time too
as i am a stundent too and my work is jsut to stick with computer thats why i choose fitness as hobby to stay fit bcz i couldnt go out and play