A big success deserves a new post!
Installed the (till now) 27 available fonts on Wiki. It took a while but from A to U (Antiqua to Ubuntu) all fonts are working!
You must believe! I did!
It took a while to "Rebuild font cache" but then I "Restart(ed) framework" and voila, my Kindle has the fonts I have chosen.
It was unclear (to me) that I had to initialize each font, one by one, and then apply the "Restart framework", but the older you get, the wiser you become.
So, long story ended , Kindle is
f o n t h a c k e d!
ixtab I owe you a beer!
EDIT: I forgot initially to select each font and, doing so, afterwords "Rebuilt font cache" and then "Restart framework".