I'm planning a couple of weeks in Italy in September, with stays in three locations: Genoa, Firenze, and Roma. We'll use trains between the three. This will be our first visit to Italy since 1988, and I would appreciate any advice from FTers on the following practical issues:

1) Does buying rail tickets by credit card from either a machine or ticket office in Italy require a PIN? [Using my "no foreign exchange fee" Chase-issued UA MP card treats PIN transactions as cash withdrawals, and applies a significant surcharge.] I found in Barcelona last year that buying transit cards with a credit card could not be done without a PIN.

2) In Firenze, I'd like to rent an automatic transmission car for two or three days, presumably from a central location, to make some day trips around Tuscany. Any words of wisdom on the practicalities of that (e.g., choice of rental company to maximize the probability that they will actually have the type of vehicle reserved, overnight parking considerations, etc.)? I have premium status with both Avis and Hertz (I've generally found the latter to be the most reliable around the world, except in the UK), but am open to other possibilities.

3) What's been the general experience regarding the security of luggage taken on board intercity trains, when too large to fit in the overhead racks? I gather there is some between-seat provision in some rail cars (but I've no idea about capacity); otherwise, it's apparently end-of-car open racks a la Amtrak. I've seen some online references to the absurdity of Americans looking to chain down their bags on these racks; and other admonitions to never let your luggage out of your sight, particularly in and around Rome's Termini station. What's the experience and the prudent middle ground here?

4) When we leave on a 06:45 departure from FCO Terminal 3, is there any advice about obtaining VAT rebate certification (should we wish to do so) before checking in our bags at around 05:00? Is the certification office open, and usable without a long line?

I'd be grateful for FTers' insights on any of the above questions. These are the sorts of things that the guidebooks don't mention, and are difficult to ascertain through online research.