So, on Earth, people get one spouse. In the afterlife, people have multiple spouses to make a myriad of spirit-babies? How many levels of the afterlife are there? Are post death marriage ceremonies and procreation described in detail?

This is actually a catch-22 with the Mormon church.  You see, Mormons actually have two marriage certificates: a legal certificate and a religious certificate.  So technically, polygamy can happen on Earth.  If a man and a woman divorce, more often than not, they are only granted a legal divorce, not a religious divorce.  If the man remarries, he is allowed to remarry without breaking the original religious bond.  Thus in heaven, the man would be married to both women.

This is also true if the wife dies.  He can remarry and be religiously married to both for heaven. 

It’s a different story for women, of course.

In the afterlife, for some reason, polygamy is required.  No one is really certain if this means that Mormons believe that more women will make it to heaven, or what, but they are told not to worry about it.

There are three levels of heaven: the Celestial Kingdom (represented by the sun), the Terrestial Kingdom (represented by the moon), and the Telestial Kingdom (represented by a star).  Mormon hell is known as Outer Darkness and is only for ex-Mormons.

The post death marriage and procreation are not described in detail.  Mormons are told that they will find out about those particulars after they die.  In fact, that’s a pretty common cop-out in Mormonism.