Having done significant traveling in Italy (and elsewhere ) I would like to suggest that you are making an endurance marathon out of what should be an inspiring period of time in one of the most beautiful and historic countries in the world. And where is Rome in your itinerary? Visiting Italy without Rome is like visiting Manhattan without Times Square.
The time it takes to get from one place to another is vastly underestimated by most travelers - it's not how long the train ride is or the flight, it's how long it takes to pack, travel to the airport or train station, wait for the train or go through security at the airport. If you do what you propose, you'll be spending almost as much time in the engagement of traveling as in absorbing the sights. Hey, Cinque Terra is great, Lake Como is great, Naples is great but you can't see that much in the time frame you have, focus on seeing deeply what you're able to. Rome could take five days on its own, every time we go there it's for five day - not only great for using reward points but gives you time to tour, walk, eat and be in a place, not through it. Venice is spectacular and won't be around much longer - it is where memories are made. Milan is outstanding and those wonderful photos barely scratched the surface. Florence is worth a month if you enjoy great art and want to delve into the history of western civilization. The hardest part of planning travel is working at limiting the number of things you're going to do in order that you can really appreciate them in the context of where they are.
To answer the question you asked, the best way to use your points IMHO is to stay five nights each in two places, taking side trips from there if you so desire. Good luck.