I did this tour in 2017. I was 71 at the time and traveling solo. Your comment about transportation being an issue because you'll be traveling solo was a little confusing to me.
I put Rome at the beginning of my trip and flew into there where I spent 6 nights in an apartment and caught up with a few of the many things I hadn't seen or done on previous trips.
From Rome I took the train to Ravenna. I stayed there 2 nights in a B&B to have the day between to visit the mosaics that aren't seen on the very short bus stop on the tour.
Then I took the train from Ravenna to Venice where I stayed 5 nights in an apartment to do my Venice catching up.
From there it was a very short train ride to Padua to arrive for the start of the tour. A few people started with extra days there which they thoroughly enjoyed.
At the end I spent 3 nights in a hotel close to the train station, took the direct train to the airport and flew back home from Milan.
Obviously, this itinerary required that I have multi-city (aka open-jaw) flight reservations. You could do the same, then take a fast train (Frecciarossa) from Rome to Padua. There are ones that take about 3.5 hours and have no train changes. They depart Roma Termini and go through Florence and Bologna. Their ultimate destination is Venice but Padua comes before Venice. Of course if you had time you could split the trip into 2 (or more) pieces/tickets with 2 nights in Florence and/or Bologna. But if Rome is calling you like it did me, I'd spend all the extra time you have before the tour in Rome.
I agree with those who weren't all that impressed with Orta and that the person in charge was rude. Breakfast was served to the RS group in 2 shifts. I was in the 2nd group. I made the mistake of going to the breakfast room too early in search of coffee and got a scolding and shooing out of the sparsely populated room. If you typically need to go back to your room after breakfast, do your best to be in the first group of RS people for breakfast!