Anyone who counts or measures keyword density really hasn't understood how this game works.
Google does not and has never had a part of its algorithm that looks at the frequency that a word or phrase appears in the text and how far above or below a mythical 'sweet spot' that is.
The way to test if your keyword density is wrong is to read what you've written, and think about how it sounds. If it sounds like natural, flowing, well-written prose then you've got it right. If it sounds like a stuck record repeating the same words over and over then you're going to bore your readers to tears, and convince them that what you've written isn't worth reading. And no matter what effect it has on your position in the search results, there's absolutely no point in being #1 if people take one look at your site and then leave so fast the door smacks their bum on the way out.