If you plan this on the same day, You don’t have a lot of time to visit anything along the way because in February days are short. The drive alone is 4.5 hours (and probably more than 5 if you factor in a restroom stop). Basically you would get on the A1 freeway at Bettolle and get off at Mestre. Also don’t discount possible adverse weather conditions (snow, fog, ice).
If you haven’t had a chance to shop at the Outlets in Foiano della Chiana, it might be a good time to do so for a couple of hours. It’s not far from the freeway entrance at Bettolle.
Florence, Bologna, Ferrara, and Padua, are all along the way (anything else you mentioned is a major detour). But even the cities above require you to get off the freeway, find your way downtown, find parking outside the ZTL, then make your way back to the freeway going north after a short visit. Assuming you don’t want to spend more than 3 or 4 hours, then I would stop in a smaller city like Ferrara or Padua.
Regarding the scenic drives unfortunately right now the A1 is the only safe route. The E45 Freeway (which you would use if you swing by Assisi or Gubbio) is closed just north of Pieve Santo Stefano near Verghereto due to emergency retrofitting work on a viaduct. All other passes may be closed because of snow and in any case they would increase your travel time significantly.
WARNING: carrying chains or having snow tires is mandatory on most roads in Tuscany and north, including the A1 freeway between Florence and Bologna from November 15 to April 15. Make all necessary arrangements with the rental company.
