I suggest you create a test library by copying a representative subset of books and then experiment with the tools and features I previously suggested. If you are using Windows you could install the Portable version and use it as a testbed, then if something breaks you can start over.
Another couple of tools you may find useful are -
Quickview and the CalibreSpy optional plugin.
Doing things in calibre is a bit like getting rid of a tree -- you could use an axe to chop it down, a chainsaw to cut it down, a dozer to push it over, or a heli-crane to pull it out
BR
PS: Or poison it with an injection of a powerful herbicide
