1 That depends on the choices. In my opinion it’s better to have a few meaningful choices rather than a lot of meaningless choices, and even better to have a bit of both. I personally tend to go for a few meaningful choices, purposely leaving out any possible smaller choices if I know in advance that those won’t really affect the overall story.
2 Definitely don’t go for the full control option!!! That’s one of the main reasons most work in progress’s tend to bleed out in a pretty early stage. Give the reader too much freedom, and you’ll end up having to write way too much. The link below is primarily a discussion about preferred gender options and orientations in games, so that might help answer some of your questions on that topic.
3 Please do not include a picture of the main character. People (me included) tend to prefer to be able to imagine what they look like for ourselves. Pictures of buildings, scenery or, if applicable, monsters, tend to be fine though. Just try to name them in such a way that any possibly visually impaired readers can get a good idea of what is depicted too. Pictures of characters other than the MC can be nice too, though I personally prefer those not to be included in the actual game, in part because I like imagining what I think they look like too, and in part because I have an ancient brick of a phone and pictures just take up a lot of space.
4 See link below
5 An overpowered main character tends to be boring, just because they can do pretty much everything they want. However, if you add some sort of glaring weakness or dark secret to such a character it might just add some meaning to their actions.
6 It’s a lot of work to code, but depending on the kind of story it could add a lot. As long as you implement save points every chapter or so the dieing part shouldn’t be too much of an issue either.