How does one hoard wealth? Am I made poorer because Bezos owns 9% of his own company?

His workers are poorer because his company's enormous valuation comes from the surplus value they produce but do not receive as compensation. You might be poorer if you own a small business those workers would frequent if they had more money.

Edit: You might also be poorer if you tried to compete with Amazon and were crushed like a bug by their anti-competitive practices.

Wrong mode of thinking. The problem is that there aren't enough alternatives. If you want an economy that is fair for workers then you need more jobs per worker so the worker can choose the best offer. That also means you want more employers, including the Jeff Bezos types.

Would this not apply to industries with lots of competition like restaurants or hotels?

Labor theory of value lmao. Amazon workers are richer because they've been given an opportunity they otherwise wouldn't have. If they could have a better job they'd take it.

trickle down economics!

How about his workers are richer because they receive a portion of the value they produce, because by combining their labor with Amazon’s capital they can produce vastly more value than without it; and if people didn’t get their share of value from producing and renting out capital they wouldn’t do it and there wouldn’t be any capital to use.

Yes you are, very much so, a multiplication of what you yourself could theoretically approach in a life-time.

Sorta. Wealth like that is control and power, and while governments theoretically have absolute power over business, actually using those powers can break things. If the government owned the same shares, you would have slightly more direct control over what Amazon does in practice. Probably. Perhaps.