I'am very glad you posted me this message. If this info is true (I didn't heart for Baron-Marquise Fonda from Genoa area by now) it is great (very important) starting point to continue with researching.
Where did you heart for him?
I was very surprised then browsed on Italian genealogy forums. I didn't found any good info about Fonda families. I think that Italians use his forum as a chat above all.
However, I will try to found more info about this person.