Yep, the margin issue is most likely wonky CSS somewhere in the book.
FWIW, my American Gods copy is just fine, but then it was originally a Kindle purchase for the anniversary re-release, so it's been through Calibre a couple times

.
EDIT: Actually, nope, on my Kobos it's
this one. (I, err, may have *quite* a few copies of American Gods lying around, including a couple good old mmpb

).
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As for the buttons, something like this should do the trick:
https://github.com/koreader/koreader/wiki/Keymapping