Great list of questions! I think I can answer a few that either were not answered or I don't think answered fully.
1 . If you go to any post that has paid out, in the address bar at the top, change "steemit" to "steemd" and it will take you to the steemd.com for that post. Just to the right of the post title on that page will be a button you can push that says "Advanced Mode" and it should be highlighted in blue. If you click that, it will give you various details of the post, including how much the post paid out, how much was paid to the author and how much was paid to curators. As well as many other interesting things like who upvoted what comments, who resteemed the post, and a few other cool things like that.
2 . To my knowledge there is currently no way to upload a video to Steemit without using Dtube or Youtube. I think those are the only options currently available.
4 . The tag "NSFW" Stands for "Not Safe For Work", and is hidden from view (unless you click it or change the option in your user settings) in case people are scrolling Steemit in a public place, like a library computer or an internet cafe or some such and don't want to offend those around them, or some people just don't want to see that kind of stuff at all.
I hope these answers help. I am unsure of the answers for questions 3 and 5.