I said this before; with ePub we're back in 1999 where the same webpage looked differently in every browser. Personally, I don't see Calibre as a reading program. Think of it more as an e-book manager, metadada editor, converter, etc. It even has some BS about transferring to various e-readers (useless feature, IMO).
Try using SVG instead of styling it in CSS - which some e-readers could very well ignore. Create those frames in Inkscape, add the text, and add them to the ePub.