You still haven't explained how there is going to be a lot of Polygamy Practiced in the Celestial Kingdom, yet there will be no Polyandry Practiced in the Celestial Kingdom, when there are 105 boys born for every 100 girls.Your error in correlation should be obvious even to you. Any consideration of birth ratio does not apply here. What does apply is the ratio of women to men in the highest degree of the CK (where marriage is practiced). If every man in that degree of the CK must be married to at least one woman, what do you think the ratio would look like?Actually, the historical birthrate does apply, since all those children who died before age 8 are automatically in the CK. So it's entirely possible that there will be more males than females in the CK.
Still doesn't work. Since polygamy and polyandry are being speculated here, it is the highest degree of the CK, not the whole CK, that is in question here. Since marriage is the only way to enter it, the birth rate does not tell us anything at all.
Since the point where spirit enters the body is not defined, you also have to factor in how many unborn that dies. There are just too many details to consider here.