If current technology barely permits survival and only permits natural population growth via throwing conventional moral standards out the window, and if there’s no reason to leave right this second, why not be patient? Spend a few decades at least in order to advance the science of human reproduction, as well as every other technology relevant to space settlement.
There will barely be people exploring the moon in 2 decades there is no chance there will be extensive settlers in space having babies in 2 decades. The whole premise and focus of this book is flawed.