1. Yes 1.8.3 is the latest Firmware.
2. There is but you would have to find the 1.8.3 Firmware zip file and download it.
I know how to manually update the firmware on the KT but I'm not SURE if it is the same for the Kobo original (I wasn't in that firmware beta group). So I don't want to give instructions that won't work (or worse
Have you had problems with the Desktop app? It goes fairly smoothly the update that way. I've updated Two Kobo 1's that way.