Hi!
Thanks for taking the time to ask about this, because I know it can seem confusing when you're posting your first story here.
In general, unless the historical figure or other fandom is forming a part of the story, it's not necessary to disclaim them. For example, if you have a scene where someone reads The Little Prince to a child at bedtime, and you haven't used the characters or storyline of that book in your tale beyond that mention of the title, you don't need to disclaim that book. If you quote a line or two from the book, you can cite it in an author's note or footnote at the end off the chapter, but it still doesn't need to be disclaimed.
Similarly, just using the name "Kagome" doesn't require you to disclaim the InuYasha fandom. Your character is not going to resemble the Kagome from InuYasha, and if the only common factor is the name, there's no crossover and therefore no need to disclaim. (Heck, I used to call my son in the playground and six other boys would answer...)
Now, if you are using elements like settings from other fandom, yes, you will need to disclaim those. You can do so in an author's note at the top of the chapter, and if you mark it as an additional disclaimer, it is not counted as part of the 600 word Author's Note limit we have per chapter. You are correct, though, that we can't allow chapters that are only an author's note, or even a disclaimer. The disclaimer, however, can be done all at the beginning of the first chapter if you wanted to do it that way. As long as the chapter also had story content, it's fine.
I hope this helps, and please feel free to ask if there's anything else we can clarify.
And welcome to AFF!