I've seen a proposal to replace interest rates with a credit tax. It would grant the us government the ability to borrow money at 0% regardless of the interest rates for the private market. This would completely destroy the belief that money is a risk free asset as governments can borrow money at any time and there is no need for government bonds anymore.

When inflation happens you raise the credit tax so that money creation actually causes net deflation once the loans are being paid back.

Not technically a fed responsibility. Taxation and spending is fiscal policy.

The fed can affect money supply by raising interest rates.