Charlotte, a Eurail pass is not your best choice, especially for Italy. Read the caution on the Rick Steves webpage about using rail passes in Italy:
https://www.ricksteves.com/travel-tips/transportation/trains/italy-rail-passes
Basically, a Eurail pass will cost you much more than simply using point-to-point tickets in Italy. For a pass covering 2 countries, you need a “Global” pass, and that will cost you $973 each (US dollars) for the 15-day consecutive day pass (the shortest term available). For only 6 travel days, a Flex pass would be $780—and that is a 7-day pass as there is no 6-day version. And then for the Frecce or “fast” trains serving routes like Florence to Rome, you need to pay extra for a seat reservation, and those are limited.
You are much better off simply buying point-to-point tickets for Italy. You can buy them either on Trenitalia or, for the journeys from Milan to Florence and Florence to Rome, you can also use the private company Italo. Their website is a bit more user-friendly to English-speakers. Tirano to Milano will be a regional train, so buy on Trenitalia. That ticket is only 12,50€. Tickets on the fast trains have a tiered pricing system; the earlier you buy the cheaper they are.
https://www.trenitalia.com/en.html
https://www.italotreno.com/en
For Switzerland, on the other hand, since you are doing longer journeys, you may want a pass of some sort. For your dates in October, you can get a good price on Saver Day Passes—-52 CHF for each of the 3 travel days you have in Switzerland. That makes a total of 156 CHF (plus reservation fees for the panoramic cars) for travel in 2d class. A regular 3-day Swiss Travel Pass would cost you 244 CHF each.
You can mix and match with First Class if you want to sit there on any of the trains—-88 CHF.
https://www.sbb.ch/en/tickets-offers/tickets/day-passes/saver-day-pass.html