When I plan a trip, I count nights on the ground. Most of the contributors here do the same.
Two nights in one place are basically one full day in that place, three nights are two full days, and so on.
Travel days are really wasted days, used for check-in, check out, pack, unpack, transfer time, getting oriented in the new place when arrived.
I like to spend at least two nights in any place and minimize one nighters as much as I can.
I’m not entirely clear on how many nights you intend to spend on the ground.
However I can tell you this:
2 nights in Venice is the minimum I recommend, 3 nights would be ideal.
Verona is probably a place where you can get away with one night only.
Lake Como (Varenna, Bellagio) deserves at least two nights, otherwise why bother.
Same with Cinque Terre. If you are traveling that far, you might as well spend a couple of nights.
You can sleep at Cinque Terre and catch a flight out of Pisa the same day, provided the flight departs in the late morning or afternoon. You need at least 1.5 - 2 hours from Monterosso to Pisa airport.
So you need a minimum of 7 nights on the ground to cover all the real estate you mention. More would be recommended.
Now back to your drawing board. Seems to me that you have barely the nights available.
