In my mind, Adobeviewer is the best ePub-reader on the Pro Pocketbooks although it is not perfect.
You can use another font with the Adobeviewer if you include this font right into the ePub/css-file.
Maybe you want to have a look at this book and its css-file
https://www.mobileread.com/forums/showthread.php?t=48377
where Zelda played a lot with the possibilities of css, amongst them using another font.