1) i don't have the 3 buttons visible, but it's been so long that i'm not sure what i did. changing launchers may be easiest
3) i installed pineapple and was able to give it accessibility access fairly easily. any chance you could add a picture of the denial page you're getting?
4) no real solution, but lift to check phone in gestures may save the step.
vlc) go to the bottom of that files page and click 'see more apps that can access all files.' vlc will be listed and you can configure storage scope from there.