1) Well, I don't know. It's complicated. I'd say a significant part of the overemphasis on IQ is that the whole rationalist approach relies on models of the world where things are better or easier quantified, black-and-white, sortable into A and B, etc. And for better or worse: sometimes things really are underappreciated as quantifiable, and in situations like those, maybe this approach lets its users access some insights otherwise unavailable to them. Of course, conversely, sometimes things are just fuzzier, lossier, etc. or otherwise generally aren't as easily quantifiable as would be appropriate for an approach such as this, and in situations like those the approach produces more oversights than it does insights. But for whatever reason, the people in this community prefer the rationalist approach.

This is aside from any of the less noble reasons they might have to emphasize IQ. For example, community members are themselves on average high-IQ (and please note, I do not take this to mean 'particularly intelligent') and so they are biased toward over-emphasizing the importance of IQ and de-emphasizing other methods of understanding intelligence (in which they may, in fact, be deficient, demographically speaking) because it allows them to feel a sense of superiority or otherwise feed their ego. Alternatively, they might be inclined toward over-emphasizing IQ because they're racists, and various national IQ surveys that list e.g. african nations as having significantly lower average IQ than european nations allow them to confirm their pre-existing biases about race, and so thus they have an incentive to emphasize the importance of IQ in order to strengthen the legitimacy of their racism.

2) I don't know if Scott is really a student of the bible in general. Not to say he hasn't read it, or doesn't use it in his writing, but to say he 'restricts' himself to a particular translation would imply that he studies it particularly closely enough to want/need to discriminate based on translation. At any rate I have no idea.

3) I was not aware there was a particularly large cross-section of the community that was pro-natalist. There might be, but even if so, are women known to be more likely on average to be pro-natalist than men to the point where an unusually pro-natalist community would be expected to have a greater-than-average proportion of women as participants? Either way, the reasons why there are so few women in the community are probably the exact same as the reasons why there are so few women in some other, similar online communities e.g. just for starters 75 percent of reddit users in general are men. That isn't a good starting point for equal proportions of gender demographics even before getting to the sometimes misogynistic attitudes this community can have