Will have a look at the other points ASAP, in the meanwhile I comment about the main topic.
If you need to use MORE categories ( I understand ) I can suggest to rename and use the Rating
pane at Contents level.
I renamed the original Category and Sub-Category fields to "IMDb Main Cat" and "IMDb Sub-Cat".
Then I renamed a custom lookup field as "Rating" in which I use the Italian values only, hence I don't download data from the IMDb when populating / updating the database.
Finally, I renamed the Original "Rating" pane to "My Categories" where I got rid of the original "rating" values and now can store as many categories as I like: IMDb gives only 2 categories anyway and I think it is wise to leave them where they are, but using this way it is possible to use many more links between movies sharing the same Categories, kind of what the Keywords pane does...
I also found out that at the IMDb the movies are often listed / categorized in a way that I don't like and using my own categories
helps much because I would change IMDb's values anyway... so I can use either the original IMDb values and my personal categories when searching, filtering, printing, browsing, etc...
Since next CATVids version will most likely work as CATraxx alreday does, it will be also possible to move i.e. the custom "My Categories" pane under the proper Library tab and have it displayed together with the "usual" Category & Sub-Category fields...
Hope this helps a little & have a nice weekend