This link explains very simply how to create epubs with new fonts:
http://dminoz.posterous.com/on-the-m...r-the-sony-650
The Kindle font is not free. It's called Caecilia. The commercially available Caecilia is not the same as the Kindle Caecilia font which has been customized.
See:
https://www.mobileread.com/forums/sho...d.php?t=115774
Lexia DaMa is similar and free:
https://www.mobileread.com/forums/sho...d.php?t=101748