The plans and prices on that website vary depending on the specific services and features you need. You'll have to visit the site to get the detailed breakdown.
One reason could be that readers on kdp.amazon.com prefer longer, more immersive reads. Short stories might not offer the same level of engagement and entertainment as longer works. Also, marketing and discoverability could be issues - they might not get as much promotion or be as easy to find among the vast selection of books.
It's hard to say exactly without further context. It could be a link to a specific post or page on Facebook, but more details are needed to determine its exact meaning.
It depends. Some people find it very useful and enjoyable for discovering new comics and interacting with fellow fans. But for others, it might not be that great.
Most likely not. www.reddit.com isn't a typical site for accessing manga like 'A Trail of Blood'. You might have better luck looking on dedicated manga websites or apps.
It varies a lot. Some authors make a decent income, while others might earn only a small amount. It depends on factors like the quality of your writing, marketing efforts, and the popularity of the genre.