No point in another FP farm. I would actually move to the forest 1N of Seoul and chop out a new worker. Obviously, slavery switch as settler moves to spot.
2nd settler will be whipped.
Pyongyang can build another buster or put hammers into stonehenge for now. Iso your gonna need all the extra gold you can scrounge.
TW next for sure. I often go Fish before POT if it has value, as it does here, since it gives a bonus anyway on POT. However, what appears to be an almost certain ISO situation, some early cottages are going to be very important. After specials, focus on shared FPs first.
The 2 hill spots with seafoods are obvious spots, but cottages and cottage growth is going to be essential here, plus close cities and tile sharing. So I'm inclined here to focus settling 3N of Seoul and 1S of marble. Both spots are close to cap and share a lot of tiles, including cottages. 3N of Seoul also has another benefit of sharing pigs at times when Seoul does not need it, plus it can get up a fast monument for fish and crabs later - a crab that can be shared with fish city later over there.(by time that city is settled it will have the crab to work immediately).
Note on monuments, if you need to build one. A nice approach if you have a forest to chop is to time, the chop to just before the invested production hits 10H (10H + 20 chop = 30H). So say say a city has two base hammers from center tile and working a forest, you can chop the turn it hits 8H (if it has another forest to switch to) or 9H if it will have no hammers to work). So 8H invest +2 base + 20H chop that turn = 30H. Basically just time it based on the base hammers the city has. Like a city on a PH may invest hammers into the monument even faster. Or you may have a 2H tile to work as well. But don't sacrifice growth unless you are in a position to get that chop, which really should always be the case when you really need a monument.
Thinking longer term here, with ISO a strong possibility, your approach to tech usually changes from normal strategies. Happiness is a oft a concern, and no happies seen yet. Monarchy could be useful to tech. You could also maybe shoot for CoL for the religion and the civic will be nice here cause you will want to pump scientists. You will also need Alpha, Maths, and IW as you focus on an Optics bulb, and later Astro. But those techs may not be urgent until later, although Alpha does allow wealth building. Another option is to use the first GS for an academy in Seoul and just tech Optics, saving 2 later GS for Astro bulb. Seoul should be a strong cap. (Note: avoid Meditation and CS)
There are stronger iso players than I though, so you may get some better advice from others.
Bottom line you want lotsa cottages early, and some cities that can run scientists.