I think it's a lot easier to fit it on a sphere than a flat land. Not only that, but rather than deciding that one civ will be in the "middle", try to:
- draw a sphere, but do not draw the equator and the poles yet
- put one civ, any civ, on the spot
- pretend that civ is the "center" on the flat representation, and then place civs on the sphere so that the relationships fit
- NOW put in the tilt of the axis of Erebus, the star, the equator, the poles, the waters, the ORBIT that Erebus revolves around...
Although there are many civs and many conditions, given the vagueness of the conditions, and hence the vast range of arrangement sets/ranges that can fall under "solution", there will only be a few outright inconsistancies.
Example: if two civs are on the opposite ends of the sphere, one can either be far North or far South of the other. You place the axis tilt, poles and orbit in after the civs, for that reason.