What subcategories do you all think would go with Castle of Fu Manchu and Mighty Jack? These two movies are fairly similar in concept (supervillain bad-guy taking over world, freezing stuff, nebulous secret agent “protagonists” that aren’t really the focus). These two seem pretty fuzzy to me.
Also - which movies would you say have the “Creepy Guy” subcategory? Devil Doll and Brain that Wouldn’t Die come to mind but I know there are others I can’t remember. 
A modest suggestion: some of these are so hard to fit into a single category that it almost seems like tags would be a better approach. The Beatniks, for example, does have a Spy/Crime plotline but could certainly be considered a Teen/Rebel movie as well. Similarly, The Skydivers is classified Teen/Rebel but revolves around a murder plot.
Using a “tags” approach might make the whole thing more flexible while at the same time making it easier to group together all the films that take place in outer space, all the films involving hypnotism/mind control, etc. etc. But as somebody who can get a little obsessed with taxonomy himself, I respect and acknowledge the hard work you’ve already put in here, so please do it how you want to do it and don’t mind me!
The trouble with categories is that they can become Byzantine very quickly.
I recommend using tags instead, that way you can define a film by context
e.g. Project Moonbase could be tagged with sci-fi and spy both genres overlap in that film and now you can find it by searching either tag or the combination of tags.
Tags are fine on teh interwebs but I’ve never seen them used in Excel. What I did was have a primary “category” that I used to put the movie in its most generic group possible then then used a “subcategory” column to describe the other significant secondary elements. Tags make it sound like something in Twitter or Instagram and I’m not sure how that would work in Excel.
I’m sure there’s a way to search metadata like tags via Advanced Filters. I’m no Excel whiz.
Tagging is preferred over categories for several reasons which is why it’s often seen in more modern software.
Excel filtering would be a quick and easy kludge for tags and tagging.
The category column can then hold a delimited list of however many tags and the header cell provides a dropdown for searching. Or equivalent. TIMTOWTDI.