1. Food. Stocking up, even on dried food items that will require added water, means
something in the order of 1kg/person/day. Two weeks supply for 2 will add up to 28kg (more than 60 pounds). In our (limited) experience, bikes have such a range that you can usually re-stock every other day, at the worst. Longer term stays in remote areas would usually require the use of a trailer. We always carry emergency food items (GORP + some rice + tuna can, enough for 1 day), and re-stock as needed.
2. Volume. My wife and I (self-supported) tour using front panniers only (Ortliebs). So, yes, it is definitely possible to carry everything inside a front+rear combo.
3. Rear rack. Is probably better used to carry food items. The problem with food is that volume and weight (usually) vary considerably over time. I much prefer to routinely pack panniers with the same items, for two reasons. First, we eventually know exactly where everything is so we do not have to rummage the find the stove. Second, once the load is balanced, we are set for the duration of the trip. We use a
bear bag to store food and secure it on top of a rear rack. Not that we have ever encountered bears, but these bags are also good at preventing squirrels/mice attacks. And it greatly simplifies odor management.