To me, several of the add-on destinations are going to get short shrift with this schedule.
There's a lot to enjoy around Lake Como, but you'll only have about 1-1/2 days there.
Bolzano can be surprisingly hot in the summer but is an attractive city with an excellent museum, and it's a gateway to the Dolomites. The area's worth considerably more than the time you'll have there.
I haven't been to Verona, but just one night anywhere feels short to me. The hassle factor is so high.
I haven't been to Modena and Parma, so I don't know whether just 3 nights allows enough time for those two side trips in addition to Bologna.
To me, there are just too many short stays here in areas with substantial sightseeing opportunities.