Regarding the first theory, i would say that.Huh... I have 2 theories now:
Since male population is lower than female, that also means male birthrate is also low.
But I doubt the few men there are would be able to sexually interact with all the possible women around (considering the title of the series mentions 1:39, I would say that it would be hard for most men to handle that many women).
But they can't either allow women to not give birth, as it would make the gender ratio situation much worse.
So, i guess most men are asked to donate their sperm to banks (which is more handable) and most women go for artificial insemination for pregnancy.
There might even be a notion that Men belong to the family, meaning a male born in a family is usually somewhat restricted to only have sex with the women in their family, possible to increase chance of inheriting genes and possibly increasing chance of male birth.
This in a way would also force other women to rely on artificial insemination more.