You can remove k for pc and install the old version. V 1.17 still works
Pretty sure I did it, a while ago ,after making a similar mistake
Just be sure to completely remove all components
A good freeware utility like Revo unnstaller, if it still exists, may help.
Otherwise you may have to manually remove some registry entries.
https://www.revouninstaller.com/revo...free-download/
Another workaround is to note that k for pc is installed as a user specific app. So if you switch to a different windows login, it will not show and you will be able to install the old version for that user. That is not a process I have tested but logically it should work, so that different users can each have access to their own Amazon accounts.
As for finding the old installer, a forum Search may help. I ask unsure of the legality of offering to upload my own backup, which I have in my Dropbox.
PM if desperate.