Is this 4 Week Italy Itinerary Crazy?

You know, when people ask "is this crazy?", the answer is almost always yes. But in your case, you have given ample time to each destination, and it does not look crazy to me in the slightest!
I would probably just add the spare nights to your other destinations (in between CT and AC). There are some nice stops (Pitigliano is one example, and I've long had Gaeta on my list), but I am not sure it is worth the hassle when those nights could be spent in any of your existing stops. Driving from the Dolomites to Amafi Coast would not be something I'd be eager to do even if I liked road trips. CT to AC is much more manageable.
I'd venture a guess that you could swim in last week of September.

For me, my preference is always public transportation. We rent cars when our itinerary isn't doable via train or bus. So, depending on car rental locations, I would return the car before Cinque Terre.

Agree with valadelphia- not crazy.

There are several fast trains and IC trains from Pisa to Salerno- change in Rome- that would be easier and probably faster than the drive. (5-6ish hours0) No need for a car in CT so I'd just get to Pisa and take train from there.
From Salerno- ferry bus or private driver to Positano.

I'd suggest staying in Salerno for those extra 2 nights- visit Paestum while there- easy train ride and Salerno itself is a great little town. Few tourists, good restaurants, nice waterfront and really fun passiegiatta.

Trip sounds well planned. I’d spend 2 nights in Orvieto. Unless you like climbing like a mountain goat, I’d stay in Amalfi vs. Positano and Amalfi is a transportation hub which would make it easier to tour the coast - ferries, buses.

Not knowing a poster’s interests makes it difficult to recommend particular cities and towns. Some would recommend either the CT or Amalfi but not both on the same trip. There are soooo many other places to enjoy in Italy and having no awareness what you’ve seen before can limit suggestions. On the way from CT south have you considered heading to Piombino and taking the ferry for some time on Elba?

Great info everyone! Philip - We've been to Italy once on a family trip and visited Rome, Venice, Milan, and then took a train from Milan north to Tirano for the Bernina Express into Switzerland. This time is just my husband and I celebrating our 20 yr anniversary and my 50th. We are going back to Rome to spend more time there and my husband wants to go to the Vatican again. The other locations are ones from my list of must sees, if I never get to go back to Italy :) We are not much for group tours, we like to explore on our own, and we love adventure, hiking, and anything water related if you couldn't tell by all of my waterfront destinations... swimming, kaying, boating, all the sun and water things. He loves to see all the churches. We'll go to museums but it's not top of our list. And of course eating a drinking, we like to sample all the foods of a region, we like to drink and socialize. Doing both CT & AC, that's just very much our thing, even if all we do is sit and look at the water, we are cool with that.

Bressanone/Brixen is an attractive town, but it's down in the valley, not up in the Dolomites. Most people here would recommend staying up in the mountains instead. Ortisei is very popular.

Should you decide to stick with Brixen, I highly recommend finding air conditioned lodging, which may not be so easy there. It can be hot down in that valley, but I guess historically there haven't been all that many days when a/c was really needed. The thing is that if you're there when it's so hot in your room that you have trouble sleeping at night, you won't really care that you're experiencing an event that used to be rare--at least I didn't when it happened to me back in 2015, in the town of Brixen (albeit not in September).

I did a quick check on the website timeanddate.com and found Brixen's high temperatures on the first seven days of September last year were 86 - 81 - 77- 86 - 86 - 90 - 82 (F).

https://www.timeanddate.com/weather/@3181550/historic?month=9&year=2022

We're all different, but for me 23 days in a row in beautiful small towns with limited cultural options would be way too many.

Although Brixen and Cortina look close on a map, but the roads in the mountains are curvy, steep and full of bicycles, so just take that into consideration when moving from the central area (Brien) to the eastern section (Cortina). Also there are a lot of buses on all the roads, as the public buses are free and encouraged to use instead of private cars. We stayed in Ortisei and it was magnificent, words and pictures do no justice to the beauty.

Also, parking in the Cinque terre is not easy and we have stayed in Sorrento which is a great hub for the Bay of Naples, Almafi coast, Naples, Pompeii and Capri/Ischia.

https://community.ricksteves.com/travel-forum/italy/italy-traffic-infringement-letter

Driving in Italy is an adventure. I wouldn't recommend it, but you seem committed, and the above discussion is interesting, especially how much income the towns make from traffic fines.

We were in Italy in May. Based on what we experienced, and feedback here, spring and fall are no longer shoulder season, so expect crowds, especially in the CT and Amalfi Coast. Positano and Amalfi town were shoulder to shoulder crowded. I frankly don't see the appeal of Positano- just high- end shops, and beaches with black dirt and pebbles, no glistening sand, as we are accustomed to at US beaches. The Positano dock was knocked out by the storms, and frequently the ferries don't run in bad weather, so we spoke with folks who couldn't get out of Positano some days to explore. The SITA buses are SRO and had hours wait for a bus with any room to pick up more passengers. Parking is an expensive nightmare.

I was amazed at the congestion in Naples, Sorrento, and the Amalfi Coast. There is no efficient , quick way to get anywhere. Infrastructure is poor, the roads small, traffic all day, diesel smells, horns and scooters everywhere. It's like taking the craziness of Rome traffic and squishing it into a much smaller area. The regional train system can barely be called a "system."

That being said, we really enjoyed staying in Sorrento and wandering around the town. Pompeii was amazing. We had unseasonably bad weather with days of rain, and there's little indoor entertainment in the AC area. However, I think Sept is usually warm and dry.

We loved Lake Como and didn't want to leave, and it was our second visit. Didn't not feel crowded there. I think I'm more drawn to northern Italy.

Many folks report lodging in the fall is expensive and in short supply. Will be interesting what you find.
Please report back as your planning evolves. We will all learn from your research. Have a great time, especially with the luxury of such a long visit.
Safe travels!