You can have diet coke, but pay attention to what it does to your body. It can stall your weight loss. Coke Zero is good, and there is a Coke Zero made with Splenda if you prefer that instead.
As for eating everything in sight: Just eat! Have snacks on hand that will help satisfy the cravings. After a while you will majorly cut back on intake without even realizing it. Have several small meals instead of 3 big ones. I like turkey roll ups as a snack. I put some cheese, sliced tomato and onion with some peperonchini (sp?) peppers inside, roll it up and enjoy. There is enough protien that it should tide you over for a while.