Need advice for last few days of trip. please

This is such a highly personal decision and as you know, the choices are endless.

I am not a Capri lover so more than a day trip would not appeal to me. Ischia is another nearby island that is supposed to be lovely but we’ve not made it there yet. Procida is charming and less touristed if you want to go somewhere not overrun. We passed a quiet Easter weekend there a few years ago. Be aware, it is very low key! Great food and wine at reasonable prices.

Ravello is an easy day trip from Positano.

Since you fly out of Rome, you need at least 1 night there, but even though you have been there before you can always find something you have not done. The light shows in the Forum perhaps? The Domus Aurea or Palazzo Valentine Domus Romano if you have not seen them. Personally, I would spend the three nights in Rome and enjoy eating all the foods I miss.

Couple of thoughts.
Maybe a night or two in Salerno and go see Paestum.
Perhaps Naples, there is much to see there.
I assume you have seen Pompeii and Herculaneum.
If you haven't been to Hadrian's Villa and night in Tivoli and visits to the villas there, including Hadrian's might be good.
Orvieto is always a good choice, Ostia Antica the day before your departure would work.
Check out some of Umbria beyond Orvieto, Terni, Spoletto, Assisi, Deruta, Todi, Montefalco, all possibilities.
Or, as Laurel suggests, do more of Rome.

I would go to Orvieto. The town is unlike any of the others you have been in so far, quieter, smaller, and the food is unique to Umbria. One of my favorite places.