If the carrying capacity of Earth really was just 35 million people, we'd have gone thru the rebound from overshoot(that is, declining population!) long, long, before the modern era(here, defined as started at around 1912 or thereabouts), and we sure as hell wouldn't have 7 billion people today.
Population overshoot may indeed be a real problem, but 35 million people is simply ridiculous(that 650,000 figure you gave for people "living like Americans", even more so). There were about 7 times that many people around when the Romans started up.and world population didn't fall at all then. It's pretty much a sure thing that population will drop at some point, after all, nobody denies that Earth's carrying capacity isn't quite infinite(of course!).
And then you don't take sociopolitical corruption and ground-level pollution into account(which is a huge problem, by the way); the former is a MAJOR reason why famines have occurred in Africa in more recent decades, and why many people CAN'T get a decent meal half the time in that area of the world and many others, and the latter may account for many of the problems in India and China as well(though there is a country in East Asia that really isn't sustainable without food imports.....and that would be Japan, which really doesn't have a lot of farmland and may be one of those areas of the world that become particularly reliant on vertical agriculture whenever that takes off.).
A much more reasonable pop. estimate for a truly sustainable Earth, with minimal famines and such under today's conditions, minus pollution and sociopolitical corruption, would be about 4-5 billion or so.