[cramoisi]

1. KOReader use a default and minimal stylesheet to style thing. This is applied before the embedded stylesheet. So you can try to disable or reenable the embedded stylesheet (bottom menu, cog , embedded style on / off) and see what you get. It would be interesting to have the book or at least the some text pages and the css file (use calibre edit book to get them).

3. you can open your stardict file in a text editor and do a lot of style inside it or you can use a lua file to do it (go for a search on github, there is at least one closed issue with that). Also, you can enable the rendering of the html if there is some inside your stardict file ; but it will display only if it's correct html. So, you're bound to edit your files anyway. The picture you provided shows clearly a bad html file (for mupdf) rendered as text.

4. With your ka1, you can switch in two colom if you are in landscape mode. You just have to edit a value in the advance options. I can tell you the way of doing it if you are interested.