I guess I tend to come down more on the nature side of nature vs. culture, but I definitely think that the possibilities you listed are entirely plausible and I'm definitely open to being convinced with well-designed, at-least-not-obviously-partisan studies.
(Amusingly, depending on what language you use, blaming "compiler bug" first when your program crashes can actually be surprisingly credible. Languages like D, for instance, which combine a strong type system with a homebrew backend overburdened with features, make it a lot more plausible than you'd think.)
I entirely agree that neither of those are existential struggles, but we still have to rank them. Personally, I'd rather lose feminist progress than liberal progress, because a liberal, open-minded society will make it a lot easier for feminism to regain ground. What good if we win equality-of-outcome, if it loses us the soul of equal rights? I believe that we ought to think that #3 if #3 is true, and that we ought to think that #2 if #2 is true. To do this, we have to be able to discern truth without bias.
Inasmuch as #3 is true, free thought and civil discourse is its ally in whole.
I also don't totally reject the notion that biology can explain differences in outcome. I just think that explanation should be a last resort after the far more likely causes of bias, random path dependency, and perverse incentives and feedback loops are ruled out. Blaming biology first is like immediately jumping to "compiler bug" when your program crashes. People who jump first to biology are probably racist or sexist.
As for immigration vs social justice: neither are IMHO existential struggles. Existial struggles are things like sustaining a modern economy post population growth and transitioning beyond fossil fuels before we either crash and burn in a Malthusian catastrophe or destroy our atmosphere and oceans. If we don't fix those things social justice and immigration issues won't matter much to the survivors of the nuclear war that ensues as global civilization collapses.
As for Trump: he is categorically unfit to be president, but Clinton was also an awful choice. That election was terrible and the lineup as a whole symptomatic of the decline of our political class.