Hi there, Confused -
I'll agree that this is a very rushed itinerary, and there's too many day trips. A couple of initial comments?
4th day - plan to do Rome to Pompeii + Amalfi coast day trip v/s Rome
to Amalfi coast day trip.
Pompeii and the Amalfi coast is a brutal day. If you are looking to do one of the bus tours that offer this one, you're looking at spending more time sitting than sightseeing: at least 3 hours each way + time to the Amalfi from Pompeii, and maybe a scant 2 hours at Pompeii...which is VAST. It's also weather-dependent, for the best experience. Say your planned day ends up to be a wet one? If you were to do it at all, I'd do it by 'fast' train to Naples and commuter train to Pompeii; same in reverse. It's faster by train, and save the Amalfi for another trip when you can give that region the time it deserves. You might also exchange Pompeii for Orvieto, as Pompeii fits so well with a Naples + Herculaneum+ Sorrento/Amalfi Coast + Capri trip.
Then go to Florence -so half day for traveling and 1 1/2 -2 days to
see Florence. Day 5 and Day 6
You'd have 1.5 days, tops, not 2. Checking out, dealing with transport, finding you new hotel, checking in, etc. takes more time than you think it will. Arriving before check-in time? You'll need to have them stow your bags. You haven't said what you plan to see in Florence but there's a ton of it on hand; 1 day plus some odd hours isn't very much for this one. Your actual travel dates are important if planning to visit the State Museums (Uffizi, Accademia, etc.) as they are closed on Mondays.
Plan to do Day trip from Florence to Cinque Terre (Tour) Day 7
If not hiking, I'd definitely scrap this for more time in Florence. It's another weather-dependent activity for best results, and a location best experienced by staying a night or two and not day-tripping it with the day-tripping mob.
Plan to see Leaning tower of Pisa (1/2 day) and go to Venice which
give 1/2 day in Venice (night 1) - Day 9 and another full day in
Venice
Pisa is not on the way to Venice. Realistically, by the time you'd pack up and head to Pisa, get to/spend time at the Piazza dei Miracoli, then get back on a train to Venice, get to hotel, etc. you will have killed most of the day. That leaves you just one day for Venice itself. You'll also be dealing with your luggage... If you feel you MUST see the tower and can give Florence more time, you might do Rome>Pisa en route to Florence> Venice instead of Rome>Florence>Pisa en route to Venice. Oh, and no, I would not even consider day-tripping Venice from Florence.
A day trip to Lake Como is another weather-dependent activity.
I guess my point is that if you can stay in locations for longer versus shorter amounts of time, you have more flexibility to work around weather and attraction closures; I mentioned State Museum closures on Mondays, the Vatican Museums are closed on Sundays, etc. What you WILL have to nail down well in advance are your advance, timed-entry reservations for the biggies, such as the Colosseum, Vatican Museums, Uffizi, etc. May is High Season so all locations promise to be very busy.
Personally, i find Rick's suggested itineraries MUCH too rushed but that's just me. It's hard to trim the plan, I know, when it's so tempting to try and see it ALL! :O)