I was trying to do a search in Category Search. When I got to Content, I found, as I have several times before, that you can only choose ONE of the options. So, 'no sex' or 'minimal sex', but not both at the same time. Or 'Much sex' and 'Stroke story'. Yes, you can select 'Any' but that's not really helpful. Not trying to get a complete rewrite of your code, but if it's possible, without too much work, I would appreciate it.
I have never had a problem checking multiple boxes for a search. The only restrictions I have noticed are that you have to check at least one box, and that you can't check "Any" + other boxes. Since neither of the prohibited combinations makes sense, this has not been a problem.
you can only choose ONE of the options
Not so. If you choose "any" then you can't choose another box, but it wouldn't make sense to do so. If you don't check "any," you can all of the others or some of the others. Any number you want.