I think there is a typo in # 10.

It reads: Using the math of game theory I proved that a couple will stop having very much sex if there is any negative cost at all to saying ‘no’ to sex.

I think, considering the following sentence, the above sentence should be:
Using the math of game theory I proved that a couple will NOT stop having very much sex if there is any negative cost at all to saying ‘no’ to sex.