Aim for less processed foods (whole grains, fruit and veggies, lean meats and beans, low-fat dairy) and watch portion control. Have broth-based soups as appetizers. Eat a fairly large salad before the main course. Small things but they make a difference.

Agreed that you should do some cardio - even a small amount makes a difference if you're not doing any yet. Walking, running, elliptical machines, stairmasters - they are all ok.

I wouldn't worry excessively about your butt if you still had it when you were a size 5 - it sounds like it will be there at any weight. So just watch yourself when you get down to your goal weight and if you keep losing past there, just up your calories to maintain the weight you like.