I'm sorry you're having to go through all this. It's not normal behavior for Pr.
It was a good idea to try a different selection in the Project panel for FCP XML export, but I'd like you to try one more. Pick a sequence, just one, in the Project panel and try to export an XML file. What happens?
Are you running Pr as an administrator?
Are all of your folder permissions correct?
Finally, it may help us if you gave very detailed information about your editing rig, including type and number of monitors.
https://community.adobe.com/t5/premiere-pro/faq-what-information-should-i-provide-when-asking-a-question-on-this-forum/td-p/3929027?page=1
For what it's worth, there is something major that's wrong with your system or with your Pr installation or with this particular project. What I hope is that it's solvable to some degree and you can get your system to either work or let you move on.
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