On number 2 and 3, the "..." you have listed could have useful information it it.
but if it says "Welcome to Kindle", then the whole bootup process has occured. On your serial console, press enter and it should ask you for a login name, just for you to check what mode you are in.
Login is disabled on the regular partition, so check the resot fo your logs for "press <something> to enter diags", and consider doing that, knc1 has the most recent post on what options to select here: "https://www.mobileread.com/forums/showthread.php?t=289497
I know there are certain triggers on when the paperwhite will 'export USB' and you can do it manually in diags mode form the command line, but I dont know why it wouldnt be showing up as a drive if you got to the "welcome to kindle" log.
Are you doing this on Linux? I know that some versions of linux without certain updates will not automatically mount the new Oasis, I wonder if that culd be possible for the PW# you have there as well. Can you list the USB VendorID and ProductID? If you are on windows those are usefult too - kindle changes product ID to DEAD sometimes. You can view that with a tool called 'USBDeview'
But you should also read through the main serial jailbreaking for dummies to learn about diags mode if you haven't already.
As for #5, I have a need for the power button off of the screen ( see attachment if what I need isn't clear ); the clicky part fell off after manhandling it in an out of the case too many times.
I wonder if you would be willing to part with it for cheap :-)
