Anonymous participant of course you'll also need to supply proof of relationship for the dependant, marriage certificate etc, or child's birth certificate etc.
No need for a rental contract, but you'll need a TM30 filed. If your landowner can't supply one then just book a night at a cheap hostel or guesthouse that files TM30 for you. Get a copy of it.
Anonymous participant you can submit a copy of your approved DTV letter/PDF as proof of the primary DTV holder when applying for the dependant DTV visa.
You don't need and can't get a sticker. The PDF mailed to you and accessable via your evisa login is your visa. Print it out. Reference the DTV visa number when submitting the application for a dependent.
Not true. But check the embassy website to ensure that the documents you submit are in a language that they accept or you may need to have them translated.