@ilovejedd
From one enthusiastic user to another:
1 - No, not that I know of. You can help code it yourself on the github page of COPS.
2 - are you using "custom columns"?
For the standard categories if it's empty/does not exist, it's skipped.
Maybe handling of "custom columns" is different or "no value" is NOT equal to "empty". (Just guessing here.)
3 - what's displayed (in my setup) is only one tag. This can be just one word or a whole list all clickable from the detailed book view.
4 - If the value is blue, you can click on it.
5 - I don't know.