He might just need more time, three days often isn't a long enough period for them to fully acclimate to totally new surroundings. It's probably worth giving him another safe space that isn't the litter box, maybe one of your moving boxes with some of your clothing in there for bedding.
Realizing that replacement is off the table for you given your rental conditions: most of the ceiling fans I've come across have readily accessible screws for cleaning or replacing the individual blades - could temporarily removing them be a solution? Give him a chance to feel confident in the space and then start putting them back as his comfort allows? In one of my old rentals it was on me to swap the blade orientation for winter/summer, but your terms are likely different than mine were.