Transfer time from Naples Centrale Circumvesuviana train to TrenItalia train in same terminal

If the Circumvesuviana is on time (and isn't canceled), yes. But I'd consider it something of a risk. Are you heading to a flight home from Rome? I wouldn't want to start my day in Sorrento in that case.

We have a flight out of Rome on the 12th and traveling to Rome by train on the 11th just to make sure we don't miss our flight. So it sounds like I should plan for the 6:00am train, but also look at the next 2 trains and the time they arrive, then base the train departure time from Naples on the latest departure from Sorrento, if that makes sense.

That 6:00 am train is the first train of the day.
One would hope it won't be delayed - but you never know!

30 min is enough for the transfer.

For time reasons, I would only use Frecciarossa service Naples-Rome. But walk-up fares are very high, and advance purchase discounts are not changeable or cancellable. So you would lose your entire ticket money if you missed such a departure. We were refused permission to take the earlier Frecciarossa, which was not full, so we sat on our luggage for an hour, rather than pay the walk-up fare and discard our tickets.

I haven't been there lately, but there have been complaints on this board about delayed Circumvesuviana trains, in 2023.

It is a long, indoor walk from lower-level Circumvesuviana to main floor Frecciarossa, but it's nice, smooth marble tiles, with an escalator up to the main floor. Are you okay with your luggage handling? The paid toilets are also on the lower level, but also a long walk. I think 7:15 arrival would be okay, but it would also be very naive to assume that this gritty, aging service will be precisely on time.

Some people might take a 130+- Euro car service from their Sorrento hotel, but that's not a low-budget option, and it's not immune to delays.

IIRC your hotel is near the ferry port/elevator?
Might be easier to take a ferry then taxi to station
I don’t think ferries typically run late-of course that would be weather dependent but I also don’t think the Sorrento-Naples ferry is often cancelled due to weather