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 - and that's not at the point were the people producing things are merelly surviving.
Capitalism really is just a way of the elites trying to get society to that sweet spot of that curve - under Capitalism 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, and because people in a Capitalist society live a bit better, are a bit less unhappy and have something to lose unlike in the outright autocratic systems, they produce more for the elites and there is less risk of rebelions so it all adds up to more profit 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.
But people do stop believing money has value, or more specifically, their trust in the value of money can go down - you all over the History in plenty of places that people's trust in the value of money can break down.
As somebody pointed out, if one person has all the money and nobody else has money, money has no value, so it's logical to expect that between were we are now and that imaginary extreme point there will be a balance in the distribution of wealth were most people do lose trust in the value of money and the "wealth" anchored on merelly that value stops being deemed wealth.
(That said, the wealthy generally move their wealth into property - as the saying goes "Buy Land: they ain't making any more of it" - but even that is backed by people's belief and society's enforcement of property laws and the mega-wealthy wouldn't be so if they had to actually protect themselves their "rights" on all that they own: the limits to wealth, when anchored down to concrete physical things that the "owners" have to defend are far far lower that the current limits on wealth based on nation-backed tokens of value and ownership)