Four countries in 17 days - question on trains etc

Why are you buying a Eurail pass? The trips outside of Switzerland are not expensive. Point to point tickets will be much cheaper than a pass. Consider flying from Zurich to Venice.

Zurich to Italy is the opportunity to train over the Bernina Pass on one of the country's most scenic train routes...either the regular train or the Bernina Express. It would make a long day to Venice, but lovely. Otherwise, fly.
Seat61 website will help with train routes, routes with sleeper cars and perhaps demystify train passes. Rick Steves also used to have an entire document about passes and when to consider them.

thank you for all your great advice!
YES we wouldn't want to miss that scenic train ride to Venice!
Ok, no Eurail pass, but point-to-point to get to and from Switzerland. Once we get to Switzerland, should we get a Swiss Travel Pass? Once we get to each town, what should we budget for getting around - Uber? busses? Cost of transit up to mountain views?

Switzerland has numerous scenic train routes. Dear 61 is bound to cover them. Rick does in his Switzerland book. Also ask on the train or Switzerland forums here. Bernina may not be ideal for Venice, but others may suggest alternatives. Also ask there about Swiss pass. There is something about half fares, so that might be an option.
As to transport, public transport is better than alot of US. Uber is not everywhere and walking is common. Venice relies on vapretto water transport

You can find most the train answers for yourself at www.seat61.com

I'd skip the day-and-a-little-bit in Rome by flying home from Venice, probably with a gateway connection that your multi-destination search function will reveal.

It appears that you'll basically have one day in Venice and 1-1/2 days in Rome. Both those are seriously inadequate, so I'd go along with applying all that time to one place. Geography argues for Venice if you want to take the Bernina Express down into Italy. Otherwise, you could fly from Switzerland to Rome.

It's quite possible, though, that there will be schedule difficulties if you try to fly home from Venice, and the fare may be quite a lot higher than from Rome.

It doesn't sound as if you've bought your airplane tickets yet. Could you add a few days so you really have time to enjoy Venice and Rome?

Thank you for all the guidance! Are the Bernia, Glacier, Golden Pass Route or Jungfraubahn trains/routes included in the Swiss Travel Pass?
Thank you!

Thank you! I will try to make this my last question: Does Swiss Travel Pass work:

from Salzburg to my first Switzerland destination?
from Zermatt (Brig) to Venice? Venice to Rome? I noticed there's a partnership with some trains in Italy.