Overpopulation would be a problem because the lack of resources, NOT the lack of space.

0/10.
but if by some chance you are actually serious. i'm sure that arsehat ian juby would love to talk with someone who has the mental capacity of pond scum.

Guys, it's ectb, it's a troll post you nonces.

The problem isn't so much fitting them.
The problem stems from an economical and survival point of view. We're already scarce on resources. Ya really think the planet could support 100x more people at once?

Not to mention OP's math implies people can live in Antarctica, swamps, volcanic regions, and humanly inhabitable places like those.

Just a few limitations:
1. there are inhabitable lands such as the polar regions and alpine terrains.
2. food would have to be grown and harvested in the oceans.
3. oxygen would run out quickly without terrestrial plants.

In your edit, your estimation of the population of the Earth is off by one order of magnitude.

People can't stand on farms where crops have to be grown, also, people can't stand where animals have to flourish, because then the animals would be dead and people would be blocking sunlight to reach crops and make them grow.

But wait can't we fit more people buy squishing humans? I mean humans are awfully light, so if we compact humans we can fit even more!