Help with Northern Italy Itinerary!

Having fallen in love with Italy on our first visit 3 years ago, we want to return in July for two weeks concentrating on Northern Italy. Having already visited Milan, Lake Como (Varenna), Venice, Manarola, Florence, Sienna and Rome, we plan to fly into Milan and travel firstly to one of the lakes...probably Lake Como again...possibly Bellagio, for 3-4 nights. Then on to Bologna for possibly 2/3 nights as we want to visit a couple of places close by, then on to Tuscany and finishing in Verona.
We'd really appreciate any advice about best places to use as a base and where is worthwhile going to see from Verona and Bologna. We love good food, but aren't necessarily 'foodies'. We do love a good glass of wine though and as such we need an itinerary that can be easily accessed by rail travel or bus...my nerves wouldn't take driving and there would be no justice in missing out on wine sampling! We appreciate a beautiful view and lovely buildings and anywhere with some cobbled streets.
So...with all of your wonderful collective knowledge, we plan to travel in a wee loop and begin and end in Milan. For a two week stay, how many nights would we need in each destination? Are we missing any wee gems that we haven't seen before? And crucially, in beautiful Tuscany, where can we base ourselves and access via public transport? We stayed in Sienna before, but barely saw the city at all as we stayed in a beautiful farmhouse out of town. If we stay the week in Tuscany should we do two bases and where are our must visits and is it possible via bus/train?
Also, my lovely husband has been quite poorly and has limited mobility, so we're just trying to make things as easy and enjoyable as possible, hence my forty million questions and need to hyper-organise.
Apologies for the lengthy ramble, but I'm very appreciative and very much looking forward to all of your suggestions and expertise!
Thanks so much in advance!