I reviewed your video. I cannot help you with your dropbox question--I am not sure what is going on with the editing issue. I would have suggested that you get an app in order to edit your spreadsheets-however, you have already done that. Many members do not realize that a separate app is required for the editing portion when opening a document from the Dropbox app.
Regarding the Apple ID password issue, some app allow the app store to be open for ~15 minutes after you have made a purchase. I know this to be true for some of the games that I play. I do not know how you would get around entering your Apple ID password. Perhaps others may know or perhaps your visit to the Apple Store will give you some good information.
Good luck and let us know what you find out.