That we somehow can't both oppose race mixing as well as other dysgenic pratices that don't involve race mixing, and shouldn't make efforts (eugenics) to counter it?

You don't need eugenics to counter it, simply stopping it by preventing race mixing and kicking out the mulattos/octaroons/non-Whites should put a stop to it. Most Whites, even in the US, are like 95+ percent White, and in a country with very few/no non-Whites and illegal race mixing that percentage will only grow over time. The average IQ in America, not separated by race, is approx. 100 and without non-Whites in the picture that number would probably be somewhere in the ballpark of 105-110.

Dissident values render active eugenic policies useless, because those on the "alt right" tend to have values that are passively eugenic anyway. Lazy negrified losers who do nothing but sit around and leech off of welfare would die out, literally or metaphorically, rendering half your argument null. We wouldn't need to prevent them from breeding because they would either be killed, locked up, or starve (or get off their ass and be useful), not to mention that such traits aren't really genetically decided anyway.

Jews just weaponize the existence of white people who are low-IQ and/or predisposed to drug addiction and alcoholism, to weaken the white race, by artificially making those types of white people reproduce more than high-quality white people.

Predisposition to vice is probably a thing, but in a society where drugs and alcohol are non existent and/or heavily restricted and policed it's a moot point.

You say it isn't entirely the Jews, but that isn't true. 90% of the issues are primarily or at least partially caused by the Jews. Laziness and vice have less to do with genetics and more to do with upbringing and societal influence. Although I'm certain these things have some genetic influence, fixing society and instilling proper values in the population is much easier and I'd wager FAR more effective than any active eugenics program could ever manage. The Jews and their extreme influence over society, degradation of values, spreading anti-ethical and anti-cultural elements like rap music and progressivism and other dogshit into society are the chief reason for White failures in the modern age (and before) and if you deny this you are implicitly anti-White and pro-Jew.

Trying to rid the White race of the problems you posed and other similar issues will only work if you attack the source of the issue. The source of the issue is not genetics, it is the Jew. Genetics are a part of it, but they are a symptom (a symptom that creates a second layer of symptoms). I agree we must end Jewish Dysgenics at all costs, but the solution is to get rid of the Jews and their lies, not further harm our birthrates and image among Whites by proving (in their eyes) the Jews' lies about fascism/the Dissident Right.

You've made blaming Jews so much the focal point of your worldview that you've come all the way round to being a radical egalitarian leftist who downplays genetic differences within the white race itself and assumes that all shortcomings within the white race must be entirely a product oppression.

Firstly, if anybody has opinions that make them similar in practice to a "radical egalitarian leftist" it's you. I'm a monarchist and do believe in strict hierarchy, but unlike you, I recognize that despite any efforts on our part, there will always be disparity and there needs to be disparity for hierarchy, and therefore society, to form. Trying to eliminate degenerate genetic influence within the White race is a good idea and should be pursued to an extent, but obsessing over minor flaws that can be solved in much better ways should not be the focus.

Jews, of course, love this because they couldn't keep weaponizing niggers against whites if niggers stopped being niggers

Whites for the most part don't act like nogs, despite the Jews best efforts. You're vastly overblowing the amount of Whites who act like this. Most Whites are semi-normal, semi-functional people, it's just that the "Florida Man" White trash are reported on more frequently so they seem like a much bigger issue than they actually are. If you compare the amount of willingly low-class, low-IQ, etc. to functioning, productive Whites the ratio is overwhelmingly in favor of the latter, and in a properly set up nation without Jewish moral, ethical, and social rot the former group would be so infinitesimal that would in effect not matter.

Was the rigorous eugenic natural selection the last Ice Age subjected our distant ancestors who entered Europe to, which was responsible for creating the white race in the first place, "messing with our genetics"?

(Assuming that the modern conception of the events are accurate,) No, because it was a natural event, not a man-made one. Active eugenics would be a man-made event and therefore would more easily bring about unintended consequences and side-effects. The more direct your interference genetics, the worse those effects become, which is one of many reasons I'm also against any significant level or gene editing.

Because my eugenics proposal would basically just emulate this Ice Age selection pressure, except maybe faster and more efficiently.

If you believe in Darwinian evolution (i.e. it takes a long ass time for even tiny changes to take place), then even making it more efficient by many times would still result in an unsustainably long-term project.