Do I love Bologna? Maybe not loooooooooove, but I have spent 3 weeks total there and I enjoy quite a few things that are IN Bologna. Not sure why I hold it against Bologna (and Milan) that the parts I am interested in are on "islands" with not-interesting-stuff in between that you have to walk or bus through. I do not hold this against Rome or Padua or Torino! I do love the porticoes and the medieval sections of town. I like your idea of a 2nd chance for Bologna.
Churches for art:
Basilica di San Domenico (closed 12:30-3:30) tomb by Nicolo Pisano & others
Basilico do San Petronio (closed 1:30–-3pm) Last Judgement frescoes (that chapel costs extra!)
Santa Maria della Vita --- see Niccolo del'Arca's Lamentation in the sanctuary & maybe go upstairs to Oratory of Santa Maria della Vita for Transit of the Virgin by Alfonso Lombardi.
Basilica di Santo Stefano (it's several churches)
San Giacomo Maggiore church + Oratorio di Santa Cecilia next door (closed 1pm-2pm)
Also:
Museo Civico Medievale (Tues-Fri 10-3pm, Sat Sun 10am-6:30pm) ---- full of first-rate interesting things including carved ivory
Pinacoteca Nazionale (closed Mon.) (good fresco cycle that shows the under-drawings)
Museo Civico Archeologico (Etruscan, Egyptian, etc.)(closed Monday)
Weekends & holidays the two main streets (Indipendenza + Rizzoli /Bassi) become completely pedestrian --- it is surprisingly fun to be a part of this crowd
Plasces to eat
Broccaindosso (we ate there for the 3rd time on our latest trip)
Osteria La Traviata
Trattoria Nonna Gigia
Lunch at Mercato di Mezzo