Seeking advice...

Sorrento is the best base for access to Positano, Capri and Pompeii.
It is faster and more convenient (as the trains have dining cars and toilets ) to take the train than to drive from Milan to Naples on the way to Sorrento.

You really don't need a car for any of those places, so it's just a matter of personal preference. I would definitely not want the car on the Amalfi Coast, but for the other places, it is not a hindrance--just not necessarily necessary.
I'd try to work it where you can end near Milan (getting to the south first before the heat gets more intense). That would require either doing an extra travel leg to Naples on your arrival day, or pressing on to Santa Margarita on the arrival day. Then flying from Naples to Milan would not be so onerous.
Sorrento is the main choice for having one base, but you could also choose Salerno. The villages at the mainland end of the Amalfi Coast are also doable, with just slightly more work.

Vietri Sul Mare is another good option. It is the most southern Amalfi coast town, and near to Salerno.

You can reach Vietri by train from Naples to Salerno then taxi or the Sitabus which operates from Salerno to Sorrento connecting all the towns.

To visit Ravello Sitabus to Amalfi then change bus to take you up to the town. Pompeii is accessed by train from Sorrento or Naples.

https://www.cnn.com/travel/article/vietri-sul-mare-amalfi-coast-italy/index.html

Yes Vietri is one of the ones I was referring to--a lot of people do not realize it has a train station and the Trenitalia train line also goes to Pompeii, but it is a short (15 minutes or so) walk from there to the site (unlike the Circumvesuviana stop, which is AT the site).
You have a longer ferry to Capri from this area though, and a bus or ferry to Salerno.

TAke into account that neither Vietri Sul Mare nor Praiano has ferry service. You would have to take a bus to another town.

Thank you all for your comments and guidance... I think we'll pass on getting a car.

Next question, are we best to get from Santa Margarita to Genoa and fly from Genoa to Naples and get to Sorrento or Amalfi or take trains?

My husband and I are traveling alone and enjoy going at our own pace. Sounds like staying in Praino can be challenging getting around without ferries and full bus's as they pass by. Do you think we should strongly consider Sorrento as a home base or Positano or split it up where we have 5 nights? Any specific hotel suggestions?

Thank you!

Hmm, I generally avoid flying in the middle of a trip, but that is a long train ride. You could fly into Naples in the morning, go to Pompeii (storing luggage), and then carry on to Positano for the rest of your trip (or book a driver to take you and wait with your luggage if that's in your budget). It's a long day but prevents you from having to change bases while also allowing you to stay on the Amalfi coast. It's really just a matter of personal preference. Plenty of people choose Sorrento and love it, but I would feel shortchanged.

I'd suggest arriving Milan, and since you're already at the airport, fly to Naples Capo Airport (NAP). Flights are available on Alitalia, Easyjet and Meridan Air. About a 2 hour flight.
From Naples take the Curreri Viaggi bus ( nice coach) to Sorrento. Timetable below. Cost €10.

https://www.curreriviaggi.it/airport-shuttle/times-download

If you plan on Positano a private driver is your best form of transportation.

Ending your AC stay train to Santa Margherita.
About 7 hrs by train or flight to Genoa. 1hr25min. Volotea airlines.

Then train to Lake Como ending in Milan for your flight home.

Gerri took the words out of my fingertips. Good plan.

What are your thoughts about splitting the 5 nights time; Perhaps 2-3 nights in Sorrento and 2-3 nights in Poisatano, Praino, Amalfi or even Vietre Sul Mare?

We're mostly interested in views, great restaurant's, some sight seeing (but not to run our selves ragged!) and meeting nice people.

Thanks!

High season--many, many tourists. Will only make it unpleasant if you don't plan for it. Views? In Sorrento (technically not on the A.C), you would need to stay down by the marina but it is a ways from the train station for day trips, either a long walk up a hill or a bus. In town near the station (around Piazza Tasso) doesn't have the best views but is far more practical, and probably less expensive too, and absolutely great, reasonable restaurants around there as well.

Check out any of Positano, Amalfi, Praiano or Vietri sul Mare on the other side. Spectacular views, but book all this stuff very soon unless you're going with what you already have reserved, and it looks like you have budget for something pretty nice.

We've decided to take your suggestion gerri, thank you. We're going to reverse our travels and fly directly on arrival from Milan to Naples on the front end. We'll stay 6 nights on the Amalfi Coast.

We'll train to Santa Margarita. Would you know if we can train from Amalfi area or do we need to head back to Sorrento?

Also, once we get to Santa Margarita, we'll spend 3 nights then onto Varenna on Lake Como for 3 nights before flying home from Milan.

Is it advisable to rent a car for this last portion of the trip or just rely on local transportation and taxis?