Nice job you people have done here.
The interior of the DF planet is not entirely solid, it is full of holes, but what is the exact ratio you get between open space and filled space in the HFS?
You have a planet with a mass of 7.7584772 * 10^21 kg based on wierd's information, and the orbital year is exactly 336 days.
Edit:
Volume is 3.879 * 10 ^ 16 m^3 based on 210km radius
Density is 167,000kg/m^3
Mass is 6.48 * 10 ^ 21 kg.
The synodic month should be longer than the Moon's sidereal month, and the moon's synodic and sidereal months happen an integer number of times per year, so there are either exactly 12 (retrograde orbit) or exactly 14 (prograde orbit) sidereal months in a year, depending on the direction the moon goes around the planet. Putting my visualisation into words there is a bit difficult.
From adventure mode, the Sun rises in the East and sets in the west as normal. The following assumes that the planet orbits around the sun in the same direction as the Earth does. To determine which direction the planet rotates in relative to the orbit around the sun, you need to know whether the planet's sidereal day is longer or shorter than the synodic day. If the synodic day is longer, then the planet rotates prograde, if the synodic day is shorter, then the planet rotates retrograde.
The sidereal period is therefor either exactly 24 or 28 days. If the sidereal period is 28 days, it is because the Moon goes around the planet in a retrograde direction, and assuming the Moon's orbit is not perfectly circular (the science people have brought up says it is not), this means tidal forces will eventually cause it to de-orbit and crash into the planet.
This is the equation for semi-major axis, assuming the Planet's mass is significantly larger than the Moon's:
(T^2) / (4*pi^2 / (G*M)) = a^3 where a is the semi-major axis
M = 7.758 * 10 ^ 21 kg
M = 6.48 * 10 ^ 21 kg
The denominator is equal to 9.134 * 10 ^ -11 somethings
If prograde orbit of 24 days:
T = 2,073,600 seconds
The semi-major axis is 38,340,280 meters = about 38,340 km 35873293.02 meters = about 35,900 km
If retrograde orbit of 28 days:
T = 2,419,200 seconds
The semi-major axis is 42,489,974.79 meters = about 42,500km 40015432.33 meters = about 40,000 km
It should be possible to determine how long until the Moon crashes into the Planet in this case.