1. There is doubt because the Fed can invoke policy to eliminate the potential for fiduciary issue. The most obvious case would be to raise the required reserve ratio to convert excess reserves into required reserves.
2. If investors see gold as a hedge against price inflation, then a dollar collapse is bullish for gold. Rising interest rates, under your scenario, are necessary to compensate for price inflation. The higher rates, then, do not imply higher real returns and thus, are not bearish for gold.