So I followed these steps and I am still not able to get the Edimax Nano connected reliably at all times. The only reliable solution is to use a powered USB hub. When using the powered USB hub, the WiFi works perfectly fine with no disconnection. I think it’s more of a hardware problem (either the 24V AC to 5V DC power conversion, or the PCB design of the BeagleBone Black), and not so much of a software problem.