It's possible, though, that this small proportion of wealth has a disproportionate effect on the political process, and then the political process has secondary effects on the wealth of non-billionaires.
To pick an extreme and unlikely hypothesis, it could be that if there weren't any billionaires corrupting politics, then the economy would be run in a better way which enabled everyone to become millionaires.
Since billionaires are a subset of those, then they cannot possibly control any more than 45%, so certainly less than half.
Can't find a source showing just billionaires, at the moment, but the first source suggests that the billionaires have a net worth on the order of 9 to 10 trillion; if billionaires control 10 trillion, and about 130 trillion is 45% of the wealth, then billionaires are in control of somewhere around 4% of global wealth.
As a rough calculation in sixty seconds, this does appear to support your assertion that billionaires control a small proportion of wealth. If you team them up with all the millionaires, they're up to almost 50%, but just the billionaires on their own; not so much.
His wealth is mostly stock, right? In fact most of the billionaires have their weight in stocks. In a theoretical situation where Bezos goes to unload all of his stocks to end world hunger, who would be there to buy it? Would the stock devalue the moment he starts selling it? It's complicated.
If you look at the data, i think you'll find that billionaires own a very small proportion of all wealth