Today the planet will generate 6,000 calories for everyone on the planet. You need 2,000, so *using today's agriculture* we could support 21 billion people.
You're forgetting all the the food that is thrown away by producers and then supermarkets because it would not sell, then all the food people buy and let go bad, and then all that they put in their plate and then throw away because they're full. So to get this 2000 calories intake farmers need to produce at least 4000. But probably you think that solving this issue is trivial.
However, a considerable amount of currently used land is used extremely inefficiently.
A no less considerable amount does not lend itself to standard agricultural practices either because of the terrain or the lack of water for irrigation. The 'efficient land use' also relies on a massive use of fossil fuel based fertilizers. But you probably think we have an inexhaustible supply of fossil fuels.
And of course the system as a whole is unbelievably inefficient because we have a meat-heavy diet. [...] And even our choice of meat is terrible; beef is far, far less efficient to produce than chicken.
Sure. Convincing everyone to stop eating beef, let alone most forms of meat, is totally realistic. And having to go down this path is absolutely not the sign that there's more people than the earth can support given our current lifestyle.
And since food costs for the average Canadian have dropped from 40% of their take-home pay to under 9% [...] we clearly have significant amounts of money we could use to pay for it,
Great! 0.5% of the population can afford increased food costs! Even if we ignore disparities among their populations and extend your reasoning to all developed countries we end up with at most a billion people. Do you even care about the remaining 85%?
So maybe the earth can sustain 7 billion people but all your arguments are naive and totally off the mark.