You lost me at Python 3 ;D.
Seriously, Python is a ginormous PITA to cross-compile. (Py3K is supposedly slightly better at that than Python 2, but nope, not really).
Also, it depends in KindleGen, of which there is no arm build, AFAIK.
You're probably better off finding a simple GTK RSS reader (in fact, that vaguely reminds me of something, someone might already have done it

).