What do you want to see and do in Florence? If Renaissance art (such as the sculptures in the Accedemia) interests you, then you should get tickets to the Uffizi as well.
I assume you're planning to get advance tickets to the Accademia. I don't think your visit there will take three hours.
I'm guessing the Ponte Vecchio will be very crowded between 5 pm and 7 pm. Maybe visit there first thing in the day, before you go to the Duomo. And it's a bridge, it shouldn't take you two hours to visit.
Piazzale Michelangelo offer a beautiful view of the city. How are you planning to get up there? We walked, but then, it was May May when we visited, and not too warm out.
You have three full days in Florence, and you're planning to visit elsewhere for 1 1/2 days of that time. I would suggest that you spend more time IN Florence, but that of course is a matter of personal preference on what you want to see in each location. From what I have heard, the Cinque Terre is VERY crowded that time of year.
I do like the way you haven't planned too much each day. That way, you'll have time to stop at a cafe for a cool drink, or sit on a bench in a small park or outside a beautiful church.
Enjoy!