Humans are animals.

Acceptable and optimal are not the same. Acceptable health with supplements, sure but there is a large gap of human harm between acceptable and optimal. You can choose that for yourself but not for others. B12 is narrow compared to the broad spectrum nutrients in food. You don't know if or what health risks you take on by being so far from the diet you evolved for and the things you are missing.

I don't actually. Preserving meat seems much more manageable to me. Vegetables and fruit are a constant pain with things like looking good on the outside then turning out to be rotten inside. Meat is just a matter of tracking the clock and freezing. That isn't a personal thing, the hassle of telling what is ripe and rotten is universal.

I'm opposed to mass feed growing to feed animals. Cows eat grass, chickens eat grubs and other bugs, pigs are amazing for turning human plant food scraps into meat. Feed is a last resort to get through winter if you are treating your animals decently.