The reserve requirements on balances on more than $115.1 million are 10%. That means with $1.56 trillion outstanding you're looking at a ballpark amount outstanding of $15 trillion in bank deposits. That's still not "much greater" than the $6 trillion annual tax revenue.

https://www.federalreserve.gov/monetarypolicy/reservereq.htm

From your link: "Depository institutions must hold reserves in the form of vault cash or deposits with Federal Reserve Banks."

Current balance of federal bank deposits is ~$2.3T:

https://www.federalreserve.gov/releases/h41/current/

Interesting. I'm not sure how to read that balance sheet. For the sake of argument let's say that there's $2.3T is federal bank deposits and $1.5T cash in circulation. If it's all used as reserve balances then that's a total of $38T in bank deposits outstanding. $6T taxing power a year is still not small compared to this!