I think ePub's can handle everything you mentioned, ePub's are just XHTML, and a subset of css [1]. Not sure about callout boxes, I don't know exactly what subset of elements are available as I've never written one, but everything else you've mentioned looks to be available [2].
Fun epub file trick: rename the file .zip, unzip -a yourbook.zip (double click unzip doesn't work on osx for me for some reason) and check out the html, css, images and xml of your book.
Fun epub file trick: rename the file .zip, unzip -a yourbook.zip (double click unzip doesn't work on osx for me for some reason) and check out the html, css, images and xml of your book.
[1] https://en.wikipedia.org/wiki/EPUB [2] https://www.w3.org/TR/2005/WD-xhtml2-20050527/elements.html