I don't know how to do it without dedrm. On the other hand, I know there are some solutions for dedrm / sideload books:
1. There's a feature in calibre's Kobo driver that you can put a file called kobo_extra.css in the device's root directory and calibre would embed its content during sending to the device, see
here.
2. About the vertical text, it's only supported by the Access engine which would only work on something called "kepub." With a plugin called "KoboTouchExtended", calibre can convert your books to kepub on the fly when sending them to your device.
3. And about margin/linespace of Japanese books, you can edit the books' locale (or just the locale in the onboard database, KoboReader.sqlite) to anything not Japanese to unlock the scrollbars, see
here.