As you are going in October (assume 2024) you will have the opportunity to visit visit the
Venice Biennale https://www.labiennale.org/en/art/2024
This is so special. I have traveled to Venice every year for the past 20 years , with exception of pandemic years and a family illness., Our stays were any where from 10 days to weeks. With all of our visits I am sure we did not see everything. With never did visit Murano but did visit Torcello for the delicious food at Locanda Cipriani.
With 2 days, suggest skipping the islands and consider staying in Canarregio district or Castello. San Marco area is always too crowded. I also recommend skipping the gondola ride and ride the #1 Vaporetto along the grand canal, A stop at the accademia will take you to the Dosedoro district (another good area to consider staying). As you get off the Vaporetto you will see signs directing you to the Peggy Guggenheim museum which is small and unconventional with a nice outdoor area., Continue walking and you arrive at Santa Maria Del Salute and also the former Customs house, There are such splendid areas to explore,