You are blowing smoke up your ass on this topic. You are not informed or looked at the issue seriously.

One thing that research shows is that poverty acts as a stimulant for reproduction in humans. We are wired for it, and it makes sense: as our immediate social group is threatened, the more there are, the more will survive. This is a mechanism polished by the ages, where the surviving carry with them the genetic recipes for the future. It may not seem to work to you, yet it does.

Conversely, the contented societies experience low growth, as it happens in Europe now. And in some social niches in the US.

You don't seem to have traveled as lot, as shown by your suggestion that in poor places the societies are not collaborative. All the contrary, go to tribal Africa or to the Amazon jungle, or to the slums of Rio or Cairo and you'll see close knit groups where the solidarity is a master rule. It is in modern America where that has gone to hell, and we see guys like Dan saying they don't give a damn about other people survival troubles.

Exceptions to the natural collaborative society can be made to transplanted/enslaved social groups, where the fabric of the millennial society is broken, and the repair isn't easy.

Where overpopulation will takes us? To the next burst of evolution, which is not predictable. We may disappear, replaced for something more adaptable to the new environment. It's the law of nature and no amount of social engineering will change it much.