Train Travel - Interlaken West to Venice to Florence to Rome

Good Afternoon,

We have the following itinerary for a certain part of the trip:

Day 1- Interlaken West to Venice in morning, 7 hour journey. Stay at night in Venice. Approx price 120 EUR

Day 2- Venice to Florence as morning as possible. 2.5 hours journey max. Approx price 55 EUR.

Same Day 2 Evening - Florence to Rome, 2.5 hours journey max. Approx price 55EUR

Last day in Rome - Roma Termini to FCO Airport. Approx price 14 EUR

1) Is there any train pass from a certain website/app that you would suggest to reduce the price/make the travel faster and more comfortable? 2) Is it better to buy now or buy at station?

3) Do I buy Interlaken-Venice ticket from SBB or Trenitalia?

Thanks!

Ps - comfort is a factor as we are a group of 12, majority seniors