I just woke up so maybe I'm not thinking straight, but can you explain to me how point number three is relevant at all? How would the the speed of a planet's rotation effect it's gravity well? I don't see how that's relevant to an orbit? Maybe you mean to somehow extrapolate the planet's size from that? I'm not sure we have enough information from the show to do that in any case. The landing party didn't seem effected by unusually heavy or weaker gravity so I suppose it's more-or-less 1G and therefore essentially Earth-sized. Maybe I'm missing the point, help me out here...
Determining the apparent rate of rotation of the planet is only for gauging how long it is taking the ship to make one lap around the planet; knowing the length of the planet's day let's you know when to say you've made one whole lap, relative to the surface of the planet. The rate of rotation of the planet doesn't determine the gravity well. Does that help?