That is probably not going to work. The USB Dongle is sending data on the RS485 protocol, not Ethernet so the adapter is not going to be compatible. I doubt that the USB dongle was affected much by the cold as it was designed with components to work at cold temps. There is a few things that you can do. I would suggest looking into a Raspberry PI to replace your computer. At around $45, it is at or below the price of your Powerlan adapters and seems to work well at cold temps. Then load FPP onto it and load your sequences onto it and it will schedule and run your show. If you put it on your home network by either wired or wireless, you can control it from any networked PC or cell phone in your house with its web interface. If the outside temps are still affecting them, since the PI is about the same size as your USB dongle, you could put them both in a box with a 20W bulb for heat and would be good to go.