And further on point 2, the limit would determined by all that people can produce as well as, on the minus side, the costs of keeping those people alive and producing.

As it so happens, people will produce more under better conditions, so spending the least amount possible keeping those people alive doesn’t yield maximum profit - there is a sweet spot somewhere in the curve were the people’s productivity minus the costs of keeping them productive is at a peak - i.e. profit is maximum.

Capitalism really is just a way of the elites trying to get society to that sweet spot of that curve - people are more productive than in overtly autocratic systems (or even further, outright slavery) were less is spent on people, they get less education and they have less freedom to (from the point of view of the elites) waste their time doing what they want rather than produce, but because people live a bit better, are a bit less unhappy and have something to lose, they produce more for the elites and there is less risk of rebelions so the whole adds up to more wealth for the elites.

As you might have noticed by now, optimizing for the sweet spot of “productivity minus costs with the riff-raff” isn’t the same as optimizing for the greatest good for the greatest number (the basic principle of the Left) since most people by a huge margin are the “riff-raff”, not the elites.