(Your link to Public education as share of GDP seems to be recursive to this post.)
Really good questions. I also wish there was better historical data, including for the many centuries of history where the one-room-schoolhouse/tutorial method dominated. Very hard to say how many people attended school in Ancient Greece, the proportion of those people relative to various demographics, or even just how big schools were.
Quick and very incomplete tidbits off the top of my head, from a combination of pitch decks and my history of education class:
I found myself nodding along to most of this and really appreciate the positive vision and integration of safety and progress. Two critical comments:
In the last section you basically assert an alternative to the supposed progress/safety tradeoff, one which I prefer. But it left unanswered (and even unasked) a lot of the live questions I have about this topic. It seems like there are broader cultural patterns of (a) overblowing or even completely manufacturing risks, and (b) decreasing our tolerance for risk in a way that is less than intentional. And these often seem like the major source of objections to a pro-progress approach!
Second: there's also a moral dimension to safety. I doubt if there's are processes that completely safeguard us from nuclear war, absent enough good people to maintain and man those processes. Our moral excellence in ongoing mastery of the natural world just does demand that we stop lagging in our mastery of ourselves; insofar as that lag is getting worse, that's a risk that's probably irreducible.
There are really two questions, I think. One is whether or not tutoring is a good way forward. The other is about the classical curriculum and methods that the tutors used, but that were also used in non-tutoring contexts (Roman primary schools, Medieval universities, etc.).
I think your info is mostly about the second thing.
Re: what changed in the Renaissance and Enlightenment: Enlightenment tutors tended to do much more geography and be more on the more aggressive side about teaching Euclid. There was also probably on average some easing up on the later elements of the trivium, with someone like Locke (qua tutoring) easing up a lot and traditionalists much less so. (You can also see some easing in De Ingenuis Moribus.)
To your point, I don't think the Renaissance works really change much about the classical approach to education. What most of your post illustrates is the extreme, multi-century stability of the Trivium approach, which was true in both tutoring and non-tutoring contexts. What's shocking about the Enlightenment is that education doesn't really look much different, except in the very upper edge of the research university context.
Part of the reason for the extreme stability of the ancient curriculum is that rhetoric was stable as the one and only master-skill of the elite, the power tool for gaining wealth and influence. That's not true anymore, which is one of many reasons to be skeptical of any sort of simple applicability of the ancient approach to today.