It is actually possible for the entire world to run out of money. Basically if money starts accumulating somewhere, either national treasury, or poor POPs that make consistently more than they spend. I think someone was able to reliably reproduce it by westernizing some specific small country. I believe the idea was that it was a country making lots of opium, so even without being in SOI and poor prestige farmers would still be exporting, but due to poor prestige and non-existing industry in said country they could not spend the money. And as money is finite (it is produced by gold mines), and prices are not adjusted according to inflation, it resulted in said farmers having so much of the worlds cash noone else had enough to afford their needs, thus making industry unable to sell their goods, thus crashing the entire economy. Basically there was not enough cash in the world for anyone to buy anything so the economy grind to a halt.
And money paid on loan interest dissapears as well, so if there is too much debt in the world, money can run out as well apparently.
But I never encountered this in either of my games, so I do not know how likely it is for this to happen on its own.
And yeah, influencing china is near immpossible, and apparently you dont want to do it anyway as they have a lot of artisans, so they could flood your market with their goods even before westernization. But you can either ignore them and go for other countries (a rubber monopoly can make you filthy rich once electronics and cars come into play), or you can conquer china for huge population gains. As for rebelions you have to pass reforms, in my last warmonger Japan game I had zero rebellions before I decided to become communist and forbade elections. Apparently POPs in Vic2 care more about ability to vote then the fact that they literally had everything else, including huge pensions (I modded them to be 5 times higher than vanilla), and very low taxes.
not to mention that laisez-faire would have crashed my economy, as several of my factories grew so large in order to provide employment to POPs that they were only barely profitable and so would go bankrupt without subsidies...