It depends on hall, but generally:
breakfast: 8:00 - 8:45
lunch: 12:30 - 1:30
dinner: 5:30 - 6:30
weekend breakfast: 9:00 - 9:45
The only meals you dont get are weekend dinner. 19 meals a week is pretty damn good.
You can get packed lunches instead of walking back to hall yes. I think you can do it for dinner too, but ive never tried