Well, on #4 I was focusing on "auto center", just go to the Custom Tag Editor in the control panel and edit the video tags, throw center tags around the embed code and wala, every time a video is posted it'll be centered.
As for images posted via file manager, to be honest I never upload images at all so I'm not really sure on the behavior... At one point I believe that once uploaded it'd be auto embedded as long as it was below a certain size, but I'm not sure of the limit offhand (or a setting).
