I second all of that, GREAT advice, Caine.
There are websites out there that do a fairly good job of calculating your daily caloric intake, as well as what to do in order to reach your goals in a healthy, realistic manner. Also, I know there has been a lot of debate about "eating what you are" in relation to your blood type, and there are some truths in it. Might be worth looking into.
Sounds like you are on the right track. 3 squares, and snacking on healthy foods, are the way to go. Incorporate veggies and fruits as snacks, and some fiber, and jump start your furnace.
Exercise, but do NOT over do it. Give your body a chance to recoup. Muscle burns fat, in turn burning calories. Cardio helps get your metabolism up, and keeps it up with the addition of health snacks and eating routine.
Biggest advise I can give, if you want something "off the plan", eat it. Everything in moderation. If you supres your urges and cravings, chances are when you DO break down, you are going to gorge yourself and over do it. Just stay realistic about things.
It is never a diet, it is a lifestyle change.