I would agree with most of the other people, cut out Sorrento and Sardinia, and then you can breathe a little bit. Your travel time isn't just how long the flight or train takes, its packing up, getting to the station/airport then getting there, getting into transport in your destination and to your next lodging. I usually take any travel day that I have and count it as a lost day because of all the logistics of getting to your next destination. I have had a few days that I have gotten to squeeze something in, but that's a bonus to me. You have 5 days out of 14 that are more or less lost.
Sorrento and Sardinia are both way too far for such a small amount of time. Both of them are "take your time and relax and then explore" types of places. I did Sardinia in 5 nights and it was STILL too short of a time to explore enough. If you do these two, you will just be running around like a chicken with your head cut off, just trying to go all these different places.
If you end up removing Sorrento (and hopefully Sardinia), I would go to Venice first, as it is farther away from Rome than everything else, and you can make your way back towards your departure city. You can extend your stays in other cities and do day trips if the mood strikes you.
Just remember, 2 nights=1 day, so the longer you can make your stays longer, it will be more enjoyable.