Asus Transformer Pad Infinity — Got my bootloader unlocked.......but...

Initially, after unlocking my bootloader, I WAS able to boot my Nexus (2012). I had the white Google logo in the middle of the screen and saw the UNLOCK icon at the bottom. It booted fine....but into 5.1

So, when I proceeded to the next steps in my attempt to downgrade to the quicker/more dependable Kit Kat, (following Kris' post on https://www.nextpit.com/how-to-downgrade-a-nexus), I must have thrown too many commands at the tablet at once......or maybe I inadvertently pulled the USB cord out in mid-file-transfer, not knowing these things sometimes take a while. (I think I lost track of my Command window and didn't see what was happening.)

Whatever happened, I am now UNABLE to boot into "normal" operating mode.

When I hit the power button, I get the Google logo OK, and the "unlocked" icon at the bottom of the screen, but I also get the Fastboot "menu tabs" at the top/right of the screen...which I can cycle through with the volume keys: (Start, Power off, Recovery mode, Restart bootloader). This menu should NOT be coming up until I hit Power/VolumeDown, right? That's the way it WAS working right after doing the unlock.

But now, that Fastboot menu comes up when I Power on. Furthermore, when I scroll into Recovery mode, (which is where I assume I need to go), then hit the Power button, it doesn't do anything. The Recovery Mode "flag" simply flashes off then back on; Restart bootloader mode lets me bring up the Android man-on-back......but that's as far as I can get. Recovery mode does nothing....goes nowhere.

Thoughts, comments? Please! Thansk.