Context is probably important here: an aristocratic female Italian character is responding to provocative insults from a female German.
The German side of it was easy: my German character is blunt and laconic, so I just peppered her dialogue with choice German words and phrases. For the Italian, I want something a little more...flowing. Like the "tirade" example on the Wikipedia article for Italian profanity
Typhoid and swans - it all comes from the same place.
Google Translate is your friend.
Nah, unless translator programs began to actually translate well when I didn't look. Try googling, however, for online curse libraries or swear-word dictionaries, I know there are things like these.
"Atheism is the religion whose followers are easiest to troll"
If you want really specific insults, try looking up forums dedicated to translating Italian.