I'm surprised your agent wasn't able to answer all of your questions about food.
But to answer them, yes, you can eat whatever, whenever, as much, and as often as you want for free! (Obviously, with the exception of the specialty restaurants.)
If you want to order room service at 7:00am (which is free, except I would provide a gratuity to the server) and then go to the buffet to eat more, you go right ahead - it's your cruise! Same thing for dinner - eat till you can't eat anymore.
And the one good thing about HAL, their food is very good, so if food is a major part of your cruise, you will have a great time!