There are night ferries from Rome (port is Civitavecchia), Naples and Salerno. Schedules won't be posted until spring.

There is luggage storage at the train station and also at the port. Overnight ferries aren't cheap (wouldn't be covered by a pass), but depends on whether you are willing to share a cabin.

A rail pass often isn't cost effective for Italy unless you are doing a lot of long distance train travel. Even then, you can often book tickets really cheap in advance on Trenitalia.

>>>Also, basically I am planning about 8 bigger train trips between cities SO should I get a rail pass or purchase these separately? They are only inside Italy. And I am happy to catch a slow train <<<

Some towns only have bus service or the bus is more convenient and faster (such as between Siena and Florence). Some towns only are served by slow trains. Fast trains operate between the major cities and don't stop at small towns. You would need to list your travel before anyone can advise you on connections. You can book discount tickets for as little as 9€ on the fast trains.

FYI - All trains in Italy except the slow R trains require seat reservations (included in the price on Trenitalia). Seats are not included with the cost of a pass so you would have that expense on top of the pass price (most seats are 10€ each).

You can go online to www.trenitalia.com and buy a super-economy ticket from Rome or Naples to Catania by daytime InterCity train from just €19, if you pre-book. Yes, train fares in Italy now work like budget airline fares! Still want a $500 pass?

There are similar cheap fares in a sleeper or couchette on the Rome/Naples-Sicily sleeper trains.

All the trains get shunted onto a train ferry to cross the Straits of Messina, a fascinating experience.

Yes, Naples Centrale has a left luggage office, no problem.