You wrote that you had installed Recue Pack (= ability to boot Kindle to diagnostics mode, and fix things). So if RP survived firmware update at worst case scenario you are still able to "downgrade" you PW2 to earlier firmware, that is if you are comfortable with SSH and Linux Terminal.
To boot into diagnostics mode you should create "ENABLE_DIAGS" file on Kindle Drive (=userstore = /mnt/us, aka what you see when you connect you Kindle to your PC), and then reboot your Kindle. It should start in diagnostics mode. If it does you've verified that you still have functional diagnostics/ Recue pack.
How to exit diagnostics mode
You can check that while you are waiting for @NiLuJe to read this thread. He will have better questions to ask you to help you know your options.
Also what build of KOreader are you using? Because there were couple of reports here about bugs causing Kindle restarts on one of the nightly build of KOreader.