All your Italian destinations are served by high speed trains. In a few hours can get anywhere from Rome without have to deal with potentially more expensive open jaw flights.
Plus train tickets can be really inexpensive if booked at least 2-3 weeks earlier.
However, being October quite far and a low season, shouldn't be much trouble to price a decent flight as per your original (and ideal) plan:
XXX-VCE/FCO-XXX.
From NAP to US you're going to pay a tad more and have to connect to FCO/CDG/AMS anyway (if Skyteam), or MUC/FRA/IST (if Star Alliance).