Well, we have sheep (+1), fish (+2 with harbor), clams (+2 with harbor), spices (+2 with grocer). Aqueduct +2, Hanging Gardens +1. Forge -1. Is that it for the pre-industrial era? We will have +3 (x2) food from clams, +4 from fish, +2 from sheep (sorry, I'm doing these numbers from memory). So that's 12 extra food and 9 health which will put us in the low 20's for population. That's not taking in to account any of the health we may get from forests.
Edit: ignoring forests, I think we have a base health of 4 (2 + 2 for freshwater). So that's 13 with a forge and accounting for resource bonuses, 12 with a factory, 10 with power, 8 with a coal plant, 6 (I think) with oil, 4 with IW. Late game health bonuses are +3 hospital, +0 supermarket... I don't think skipping National Park is really an option given the fact that we can't trade for health resources...