Anything with a value that fluctuates against the dollar is a commodity. Coupons are a currency because they are denominated in dollars and have a specified dollar value that never varies, albeit very small.

Banks actually do create dollars, but only within the reserve system. By creating a debt account/instrument for the borrower as their asset they are able to balance that against created currency without actually increasing the “net” money supply. The dollars they create are the bank’s “debt”. As the borrower pays the principal down the dollars the bank created are extinguished to remain in balance. One entity’s debt is always another’s asset.

These are things I’m fairly certain of because I learned them from some top economists who have worked within the Federal Reserve system. One was an advisor to the Senate Budget Committee.