As painful as it is, I believe the dark age will continue another 5+ turns. Besides finishing factory/coal in all major cities, in those that already have coal plant, I'd like to build 50 settlers, 25 mining, and 25 sushi over this span of turns. Along with 100 triremes, but the non-factory islands can help here.
I'll probably get some explorers out of it too because I'll use them to get overflow and build settlers in 1t with no whipping
10 settlers for seafood islands, 15 settlers remain on my transports, and 25 will settle the mainland. The first settlers I produce will prioritize settling the mainland, squeezed in all over, so they can get mining and sushi at 5 cities per turn. Oh yea, this will require 510gpt
These new cities will build Terrace (4t), then explorers (2t) at ~45hpt. Nothing else except eventually research. They will work very few tiles, if any. Just add new scientists with new population. This will free up my super-cities to do research.
I'll probably get some explorers out of it too because I'll use them to get overflow and build settlers in 1t with no whipping

10 settlers for seafood islands, 15 settlers remain on my transports, and 25 will settle the mainland. The first settlers I produce will prioritize settling the mainland, squeezed in all over, so they can get mining and sushi at 5 cities per turn. Oh yea, this will require 510gpt

These new cities will build Terrace (4t), then explorers (2t) at ~45hpt. Nothing else except eventually research. They will work very few tiles, if any. Just add new scientists with new population. This will free up my super-cities to do research.