This images show how I have the COM3 port configured in Windows and how I have Putty configured. I believe that this matches the instructions of the tutorial.
With USB power disconnected, I pull the battery, count to five, reconnect the battery (but not USB power). No indication of booting in terminal or otherwise. Next I hold the power button down until I get four flashes on the LED. Still no indication of booting.
I know that the power button physically works (as in power connected, power not connected) because holding it down causes the charging LED to flash four times. It's doing something. It's not like the power button is physically broken. However, I can't seem to get this thing to boot up to the point where output should be written to the Terminal screen. Obviously a bricked device never fully boots up (duh), but maybe my Kindle is crapping out so early in the boot that it freezes up before it even gets to the point where characters should be written to the screen.
The only other thing I can think of to try is to pull a battery from another Kindle and see if it makes any difference. But since I check voltages on this battery before (reported previously) I would not expect that to change anything.
Still stumped, but grateful for your help.
Edited to change images.