Note that you cannot re-enter Pompeii Scavi with a same-day ticket. So you either eat at the (satisfactory) glorified cafeteria inside, or eat before or after your visit. We don't use guides, so I can't help with your main question. We spent 6-8 hours, under rather hot late May conditions. But our day, the Villa of the Mysteries was open, and this requires a lot of extra walking time. There are a couple of hotels near the Circumvesuviana entrance (Porta Marina), but it's not a dining area. Note that Pompeii Scavi is only a small part of the modern, bustling city of [modern] Pompeii. As you suggest, most people stay in Sorrento or Naples to visit Pompeii without luggage. But there is good luggage storage at the Scavi entrance. I think it's free.
The comment about the Naples museum is interesting. I love museums, but I agree that more time in Pompeii Scavi is more important than seeing the Brothel frescoes and original art brought indoors for conservation. OPINION. BTW, the Farnese Marbles are also in that museum, really important sculptures.