I think the idea is to start by destroying the fiat banking system...

That worked so well for Argentina...

A better system is do away with income tax, and only have a resource tax including land, i.e. land value tax + sales tax + resources extracted from the earth tax. This tax should be high enough to guarantee healthcare, education, food, housing, water to every citizen.

A bigger safety net will get more people into college or careers so they'll be too busy to have kids for awhile, and will start a family in their 30s and then maybe only have two kids, if people are slaves to wage then they almost have to get married early to even afford a place to live and that often leads to children not long after.

A comfortable and happy society is a well balanced society and will have more natural population i.e. something close to repopulation quotient.

I don't have stats on this but maybe compare countries like the USA with Finland, and Denmark which often rank top 10 on 'happy countries' lists.

You don't need to have a high HDI society with free market principles and individual civil liberties. The requirements for limiting population are even lower. You just need to eradicate extreme poverty and provide decent healthcare and education. Most countries in the world are already on the path to meet these requirements (including major ones). Birth rates are in free fall across the world [1]. There's no one to get on board with "my ideals".

[1] https://www.youtube.com/watch?v=QsBT5EQt348