If you replace the 60A, 240V breaker with the appropriate single breaker, for the feeds conductor size, which appears to be #12, so a 20A should suffice, however, check to see how the romex is labeled.If there is no need for 240v the feed it could be converted to 120v at the main panel to solve the wiring problem.
There is a whole procedure involving neutrals and alternative grnding for sub-panels, designed to ensure safety.