No problem for your Nuvi in getting files if GarminDevice.xml is in Garmin folder..
You can run Webupdater just having a GarminDevice.xml in a Garmin folder in a pedrive and get all the needed files,
having Garmin USB drivers installed on pc.
So install them, attach your nuvi USB and start Webupdater.

Kunix's cure is made for non starting nuvis, your nuvi starts, you just need probably txt files as Lolypop wrote.
Edit:I see you already used Kunix's cure, how did you format Nuvi?