If you must do this ... don't. (Sigh.)
Consider using a wired, commercial Access Point (a bridge between wired and wireless Ethernet) rather than any sort of USB dongle designed for workstations. An external AP device should have one or more external antennas and a maximum output wattage which may improve datalink connectivity. It won't eliminate errors and their resulting problems, but it should produce better results. Your odds of being able to get a client to read and write any files will be significantly greater then if you try to use a USB dongle on your server.
An external AP won't make NFS function well. But it might make NFS functional.
Additionally, be sure to test NFS over TCP as well as over UDP. Since you will have continuous errors, timeouts, and retransmissions, you may obtain better results moving retry operations into the network protocol stack.