I've done what you're suggesting. It's a decent start for a marketing strategy, but as far as doing it just to make money, it doesn't work. Here's why. If your story is under 10,000 words people will feel ripped off at anything higher than .99 cents. Of that you keep around .30 or .35 cents. (It's been awhile since I've done it that way.) So, you need to sell 3 'books' to make $1. That's 60 books a month to make less than $20. I fell when I sell 60 books, I should get close to $60. (at least.) That's not going to happen with a single short story. However Novellas, (30,000-50,000 words) are making comeback. (They usually start at around $2.99, and up to 70% of that can be yours through KDP) I did want to mention that I have some friends that do the .99 cent short story thing as part of a marketing strategy and they do with very well with it. But they understand these types of books are a 'loss leader'.
Depends on the genre. Erotica, for example, seems OK with short stories at $2.99. Also, if you're willing to be Amazon-exclusive, they currently pay about $2 every time someone borrows a short story and reads 10% of it. But that can't last as I can't see it makes any financial sense for them.
Hmm...I've been considering a short story collection for some time myself. The only thing about mine is it would be mixing 3 genres. Sci-fi, horror, and sword and sorcery/fantasy. Just to give readers a wide spectrum to sample from what I can write. Not sure if mixing genres would be wise or not. Still gotta get the stories finished first haha
I have, through an e-book publisher. It's sold for 3,96, which sounds like a lot but it seems to have sold a few copies. I'm currently waiting to hear exactly how many in the next week or so. It's 14 pages. Here they call it an "e-single", somewhat like the kindle version, and where I live you can also read these at the "e-library" for free (but every download pays the author a smaller amount too). I think it's something I could consider doing again.
I think single stories are a better way to sell than anthologies using ebooks. I've bought a fair few short works, all single stories, mostly travelogues and adventure tales. I think it's great.
Flash fiction? Personally I don't think anyone would pay for that. I know I wouldn't. You'd do better posting them on your blog or something as a way of raising interest for your longer stories.
No, that's pushing it a bit far. The process of buying it wouldn't be worth it. I mean, you could fit the whole story in the review!