When you tried plugging in to use flasher -i did you try keeping power button depressed for 10 seconds, until you got that faint vibration which ensures that device is really off?
Crazily recently had N9 that ATF Nitro box couldn't recover, but earlier version of Lumia Software Recovery Tool did identify strangely.
You are lucky if Nokia Care will look at it, in UK as N9 was never marketed we were on our own with any issues!