I have mostly done ebooks by taking the original Word document, saving it as HTML in Word, then converting that with Calibre to give me an epub. Then I rweak the epub with Sigil.
When you do that, Calibre puts a lot of code into the epub. At the very beginning (in the first HTML file inside the epub), it puts a ton of font-face items, many which I delete, but I leave ones I want to use. They look like this:
font-family: Courier New
Then in the css file, it puts entries like this:
font-family: "Courier New";
If you then use that css definition in the html for a particular page, it will take effect, as long as you do not override it with the font setting on the Nook - i.e. use Publisher Default.
This has worked for me.