For the CSV, I recommend looking into the
Import List plugin.
Since you've OCR'd your PDF files,
Power Search may possibly be worth the effort of setup.
Admittedly, I only skimmed the rest of the post, but I suspect the
View Manager plugin may also be of some use -- it'll let you swap between different columnsets.
Also, look into User Categories. Basically combining selected categories from
any column and group them all together in the tag browser.
For a more concrete example, say you have taglike columns #songs and #albums and #musicians, you can then group 'Stairway to Heaven' and 'Led Zeppelin IV' and 'Robert Plant' under the same @Led Zeppelin usercat.