Train to Milan, that's fine too, if time spend 2 nights in lake come specifically in bellagio or lak

Thanks for your feedback. We are planning on flying to the UK after our stop in Venice, but I thought it would be a good idea to fly from Milan to see the city. However, I will look into flying out of Venice. I'm open to seeing Florence as well, but just very confused on how to plan my time out in Tuscany and now Florence. Thanks again!
Second the suggestion to fly out of Venice. I'd drop Milan, the CT unless you like to hike), and add more time in Florence and travelling to Venice cheapest flight tickets from sfo to washington dc by stopping at some of the smaller cities in route. Three nites in Venice is preferable to two.
I also not not understand your itinerary. You're spending 1 night in Cinque Terre and then taking a train from Florence to Venice? How are you getting to Florence? Why not take a train from La Spezia which goes to Venice via Florence?
Rome (3 nights) 2 nights more than enough, two 4 hours half day trips to Vatican and historical sites (book guided tour for both' viator.com ) spend evening at Spanish steps and Trevi fountain, and enjoy the historic walks with great food.
Train to Milan, that's fine too, if time spend 2 nights in lake come specifically in bellagio or lake Garda and a guided tour to Verona from Garda or you can book day trips From Milan, como departs everyday and lake Garda and Verona every Friday only. Hopefully it works out for you.
I would delete CT and Milan from this itinerary. You haven't included enough time to appreciate either. It is not exactly clear how many nights you have but you might consider 3 nights in Rome and 4 in Tuscany. If you have a car stay in the Tuscan countryside and take day trips to Pisa, Siena, San Gimignano and Florence (bus). If you don't want to rent a car, stay in Florence and take day trips to the countryside by bus. Then train to Venice from Florence, stay 3 nights and fly out of Venice.