I don't know Gloucester specifically (I know Cape Cod far better), but for that general area, this is excellent striper and bluefish season. Looking at Google Maps, I don't see many jetties, and I see lots of what appear to be fairly steep cliff type structures that would probably provide access challenges. Given your limited time, I would try to stick to the estuaries/canals if you can't find better intel on specific productive open water areas accessible from shore.
Wingaersheek Beach looks pretty promising. It looks like there's good access to the estuary with easy access to dropoffs (hard to judge from maps, though), plus some open beach area to scan for flocks of birds working bait on the surface, which means you'll have pods of fish below. That area also looks like it might have some large tide swings (thanks to the street view photo spheres), which means there's a chance you could find some good action around sand bars (especially cuts between sand bars) if it is high tide and dropping. Be careful wading though. Another interesting area is
Salt Island, right off Good Harbor Beach. It looks like there's access from land, but hard to tell. Also tough to tell if it's really fishable on the fishy-looking side. This seems to be a high risk, high reward situation for your limited time.
I would recommend your 9 weight. 8 weight will make your life miserable if its windy. Plus, the BIG fish should be in by now. We're approaching the time where a 10 lb striper is trash. The majority of fishing you'll do will be subsurface, unless you get lucky and find a pod of fish working bait up top. There's almost never a circumstance that a chartruese and white clouser won't work, though. Sand eel patterns and deceivers will also work well. Hard for me to recommend how fast of a sinking of line is ideal for that area since I don't know depths or currents there. Bring some heavy shock tippet or wire leader. If you get into some bluefish, they have nasty teeth and will slice through 20 lb mono with no problem.