welcome to the cruise-chat. I hope you will always find waht you are surching for.
To your question: I believe it is impossible to see Capri, Sorrento, Amalfi coast, Positano and Pompeji between 8 AM and 6 PM. You need a whole day for Capri, Sorrento and Pompeji. In the European Port Chat you will find a lot fof hints therefore.
Click here for more information:
The ferries timetable from/to Amalfi:
Have a nice day in Naples and around