So, we're creating a culture in which the only way to be modern and have a high standard of living is for society not to have enough children. Suppose this success continues, and in 2300 the human population goes below one billion. Can you envision how humanity will start to both (1) retain a high standard of living, and (2) have more children?

Yes, we have too many people right now for the planet. There's a quick fix: Start settling space.