@Doonge,
I use this
'Modify CSS' option from the KoboTouch driver. I mainly send standard epubs rather than kepubs. I think it's also available in the KoboTouchExtended driver.
There are also some css-related patches available in the
Kobo Patcher (some for epubs, some for kepubs) which may be of interest to you.
I don't think any of the above is going to be much use for those css pseudo items though. You might have better luck with SmallCaps. With some manual effort (per book) it is possible to get the Kobo to display a proper SmallCaps font (which you'd need to sideload first) without resorting to embedding fonts in every book.