Why would a simplified simulation of Gravity be needed? And why do two different people ask about this specific thing within less than a week?!
Apart from hardcoding the Gravity a few kilometers close to the Surface for sanity sake, the Formula of Gravity for a Torus is super easy to do because the Torus is supposed to have symmetric Mass.
What is Foucault’s Law? Wikipedia gives me very morally questionable results for that one, due to what I presume to be naming coincidences.
Seasons and Ocean Levels will be pre-computed, to prevent Lag, so you can’t really change them by throwing an additional Moon towards the Area.