Password to the 'main' operating system has been disabled, well, like in forever on a PW3.
The passwords you are generating are for the 'diags' operating system.
Use ssh or telnet over USB cable, no passwords required.
If you simply must ssh in over Wifi, use pub-key authentication.
Your Kindle is running 5.4.2? Then
it is not a PW-3.
Use the device's serial number and our model number table to find out it's proper nickname here.
No, that thread is for a PW-2 and it is not maintained.
Use the maintained thread:
https://www.mobileread.com/forums/sho...d.php?t=275877
(See Step #1 for how to id your kindle model)