Your thoughts are great, but I'm afraid 6hrs is not enough time in my opinion. You will take a taxi, then perhaps go to Isla Verde or Carolina and spend money in a nearby restaurant/store, then head to airport and go through security. The nearby areas are not that bad, is more inland that is a bit problematic. Mind you, some businesses have been shut down due to damages, but others have opened up. Me, I will opt to hire a taxi for the time being, go to Piñones, which is 15 minutes or so car ride, grab some local cuisine, alcapurrias, píononos, bacalaito, etc. these are local fried food. There are kiosk along the beach where you can grab them, enjoy the scenery, some of the kiosks have opened up and are operating. Offer to buy some food to the taxi driver as well and head back to airport.