For number 1 and 2, harm reduction:
Animals definitely do eat a lot more plants than people do, and thus rely on larger quantities of plant matter before human consumption of the animal. But most of that plant matter is inedible to humans and is a byproduct of human farming.
Yeah. A ton of material from soybeans goes to animals. Some of it is the actual soybeans, themselves. But most of it is stalks, leaves, seed pods, and other feed material.
Here's Cattle Feed for Energy:
Citrus Pulp, for example, is the remnants of an orange left behind after it has been juiced. Hulls are the shells the soybean itself is in. Wheat middlings are the leftover material of wheat otherwise pounded to flour. Humans can eat corn, obviously, and molasses, and oats... but those make up a relatively small portion of what's actually fed to cows.
Here's the Protein Feeds for cattle:
Again, mostly things humans don't eat. Peanut Meal and Soybean Meal are what is left behind after Soy Oil and Peanut Oil have been extracted from the material. And Cottonseed is a secondary output of fabric and clothing industries.
Finally, here's the roughage that cows eat:
As you can see, all stuff that isn't consumable by humans, and all byproducts of human farming.
The vast majority of what cows eat is stuff humans would otherwise discard as waste from other processes we'd still follow through on in a Vegan culture.
So all the harm to plants would still exist, only now massive quantities of additional food waste would occur. And also there wouldn't be cows for very long... Because if we're not breeding and feeding and farming them, they wouldn't survive in the wilds well at -all-.
Chickens? Same thing. Soybean, Corn, and Wheat Meal make up the bulk of their diet for protein. Fats tend to be various vegetable oils or pig and beef fat added to the meal. And while they are, often, given grains to eat... those are typically byproducts of the brewing industry.
So once again just massive piles of wasted plant matter rotting away, and the likely extinction of the species.
Harm Reduction is nice as a theory, and people point to the food that animals eat as a way to say that the amount of crops would be smaller... But they wouldn't. They'd be -bigger-. They'd have to be.
Because right now we're using food-waste filled animals to take up a huge portion of our caloric intake. Without that we'd need a much larger quantity of plant farming than we already have in order to sustain the populous. And without animal farming techniques we'd have no use for the rest of the plant matter generated to consume just the nutrient-dense portion we desire.
6 million metric tons of soybeans were consumed by humans. 35.8 million metric tons of soy plant matter were consumed by cattle. Without cattle, we'd just have 35.8 million metric tons of soybean plant waste.
Only without beef, we'd also need -vastly- more metric tons of soybeans to sustain the populace, and since only about 1/7th of the plant is human-consumable...
It'd just be more waste. Killing vastly more plants and letting the majority of their bodies rot away.
It's a beautiful lie that we feed animals most of the soybeans we harvest. But it is a lie.
As to 3: I'm glad you acknowledge people's difficulties and that some people would find it utterly impossible to safely be Vegan.
But if we tried to make our society "Go Vegan", which is largely the hope for most Vegans in their desire to 'reduce harm' or otherwise protect animals from use as tools or slaughtered, what the hell would those people -do- to survive? Like you acknowledge the problem exists, and then gloss over it to say "But MOST people wouldn't have that problem." as if it is irrelevant to the calculous. I guess those folks just get to suffer and die, then, for the moral superiority of a Vegan society.
Anyway. Eating animals and plants reduces the total amount of harm in pure numbers because of the quantity of plants that would need to die to sustain humanity being far larger than it already is, and our use of the non-human-comestible plant matter to feed animals for for later consumption means that a smaller number of animals than plants need to suffer to sustain our society.
Vegans and other humans ultimately have to place a hierarchy on what life it is acceptable to take to continue existing. Most vegans do so from a place of ignorance, however, thanks to beautiful lies.
The lie that a plant is an unthinking, unexperiencing, unaware philosophical zombie, the lie that most of our edible harvest goes to animals for slaughter, the lie that you'll be healthier in many respects and face no danger in others, the lie that going vegan will help impoverished farmers in South America and protect the rain forests, the lie that veganism will somehow reduce water use worldwide and help everyone have access to clean and pure water.
To be clear, I literally looked at the "Why go Vegan?" page of The Vegan Society's website for those last ones. I went to their webpage because in 1945 they were the founders of Veganism as a concept. Their founder, David Watson, also famously expressed that his Veganism was a direct rebuke of exploitation of animals. Hence why he founded it: It was a non-dairy vegetarianism. Since 1951 their doctrine has been "Man should live without exploiting animals". (No harm reduction involved, just no animal exploitation)
I've already explained why it won't protect the rainforest or impoverished farmers as we need WAY MORE LAND to support everyone, not less. And reducing water use in animal farms won't magically provide clean drinking water to the masses who don't have access mainly due to local industry pollution or relative geographic isolation from extant facilities.
And the health benefits have been overblown since the 1800s when people claimed vegetarianism would cure everything from acne to tuberculosis.
TLDR: Most of what we feed to animals is byproducts from other human consumption that would be wasted otherwise, and you've been lied to for years, even decades, by Vegan websites and authorities who either made broad assumptions without deeper research, or just as likely found out the truth and made the decision that their personal moral stance on killing animals was more important than intellectual honesty.
I'm totally fine with vegetarianism and vegetarian diets. But the -push- of Veganism and the lies it spreads will be the death of so, so, many people, and the extinction of entire species of animals and plants.
As far as who will create the nutrient dense foods that do not rely on exploitation? Nerds. Nerds who love science fiction so much they eventually create some kind of food synthesizer.
Until then, harm reduction means eating meat and plants in appropriate proportions while trying to maintain an ecological niche that is quickly being destroyed by shit -outside- of food... Rather than obsessing about the consumption of animals in our society.
Advocate for pollution protections, industry controls, desalination plant expansion, clean energy, an international standard on food and water as human rights rather than commodities to be traded and sold.
You can't ethically consume plants your way out of the problems we have. No one can. And it doesn't reduce harm, it just shifts it around a little so plants suffer slightly more and cows suffer slightly less. All while human suffering just increases.
