How does Polygon tokenomics work?

I have been researching some ETH L2 projects and I am confused at how Polygon's tokenomics work. Can someone explain?

Currently it seems the tx cost is approximately $.00004. There have been about 21 million transactions on Polygon based on the blockexplorer. That means Polygon has generated $840 ($5-10 a day) in network fees to date.

The staking reward for tokenholders seems to be about 15%-20%. Where is the money coming from?

It seems that more and more tokens are being issued out of thin air to reward stakers without generating any network fees. How is this sustainable?

Even if more and more projects use Polygon, the number of transactions on the network doesn't seem to have any bearing on the staking rewards. For example, if the network increased the number of transactions by 100x or 1000x, the network would only be generating $500 or $5000 a day in fees. It seems insignificant compared to the number of tokens out there.

Am I missing something?

Also, is Polygon even actually scaling Ethereum? most of the projects building on Polygon seem to only be using it cause its basically free to use. theres no way to confirm if any of the transactions are "real" because anyone can just spam transactions to inflate its numbers. the transactions likely would have never been on Ethereum in the first place, and it seems to be its own thing without any real connection to Ethereum except a bridge.