Adding supplements like protein powders, creatine monohydrate and digestive enzymes will surely help, but it's best that you control what and how much you eat, otherwise it's kinda like shooting in the dark.
You should definitely check out the diet and nutrition section on exrx.net,also www.johnberardi.com
.As for books,I can't recommend one for football players specifically, but you can try Bottomline Bodybuilding by Nelson Montana(feel free to skip the steroid sections :P).You should check out the books on exrx, maybe you'll find something.
You'll have to set caloric intake, macronutrient ratios (protein/fat/carbohydrates) according to your weight, bodyfat%,activity and goals.
Don't restrict fat/carbs intake too much, eat most of your carbs from fresh fruit and veggies(-later edit- so that you'll add some alkaline foods to counter acid producing ones like meat, dairy products, cereals ... that's about everything other than fruit and veggies-end edit-), eat nuts and seeds (i'm assuming you'll watch your calories- these are quite dense calorie-wise) like wallnuts, flax seeds, EAT WHOLE(animal) PROTEIN WITH EVERY MEAL, about 1.3 grams of protein per lb of lean bodyweight.
Planning your diet can get quite boring, but it's well worth the time.
About the metabolic diet( it's Di Pasquale's, right?) - I've tried it too, but i've gotten fat on it.But i didn't manage to restrict my carb intake enough, nor do any aerobics.