Can you please add temporary FTP and administrator access, so I can check the issues directly and debug them?
1. Does this happen on a specific browser? There are no known issues there at the moment. It might be related to a browser plugin, or something similar.
1. I was able to access the back-end no problem. Let me know if this happens on a specific browsers only.
2. Make sure that this option is set to the default OFF. When this is enabled, then items, that does not have a relation to the taxonomy will be displayed.
Also, you can set a default value to the filters as the “Choose one option” here – so that by default the filters are not active unless the user triggers a change.
These should make it work.