- I don't have time to look up the research on this stuff, I know that last I checked the first point is documented on the wikipedia page for veganism (i.e. It links to the statement by the dietetic orgs).
- It's not hard or very costly to get from those to a complete diet without animal products
- I don't know enough about to say with certainty, but I'm pretty sure most farmland is not grazed.
- should be pretty easy to find info on, look up how much of our crops go to animal feed. If I'm wrong I'm happy to read studies that show we don't do that, but the studies I've read inform my position. Due to how trophic levels work, animal products are always going to be an inefficient source of calories