....My only questions are the following:
1) How long does it take to get to Nice from Florence by train?
MY GUESS IS ABOUT 5 HOURS

2) Is it worth a 3 hour stop in Pisa for the tower?
NO

3) Would a stop between Florence and Nice be required because of long train ride?
NO

4) How to get cheapest flight to Rome from Paris
EasyJet from Orly Very cheap, but plane goes
very early - flight 4247 dep. 06:00, arr. 08:00