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None of the studies or reviews of studies you cited supports the idea that the claim is absurd. In fact, they tend to support the general findings of the study:

Here is the link to the WA PO article about it: https://www.washingtonpost.com/news/fact-checker/wp/2014/05/01/one-in-five-women-in-college-sexually-assaulted-the-source-of-this-statistic/

Wa Po goes through the data and says essentially the exact thing I said in my prior post (data is inconclusive, but 1 in 5 seems about right from the data presented. We just aren't sure whether that study can be generalized to the population as a whole).

The NIJ says this: “Regardless of which studies are most accurate, the often-quoted statistic that one in four American college women will be raped during her college years is not supported by the scientific evidence. Nonetheless, several studies indicate that a substantial proportion of female students — between 18 and 20 percent — experience rape or some other form of sexual assault during their college years.” Note that 18-20% is about 1 in 5.

You are right that the Christina Hoff Sommers and Asche Schow articles have HEADLINES claiming something like "NO, 1 IN 5 WOMEN HAVE NOT BEEN RAPED ON COLLEGE CAMPUSES" (which, by the way, was not the claim of the study, or Obama when he mentioned this, or of the person quoting it here), but the strongest claims made by the articles themselves don't say that at all. They are that "But in reality, this claim is misleading at best." They then do things poorly: 1. They mention problems with the representativeness of the original study which is the exact weakness described by the authors of the study and recognized by WA PO and claim that because of that weakness the claim is misleading, and 2. they argued about the wording of the questions in the study themselves but suggested solutions that would make for an even worse study. But even if they are absolutely right that there are some problems with the study, it doesn't mean that the incidence of sexual assault is lower than the study found, it only means that we aren't totally sure.

And the fact that multiple studies indicate similar numbers (about 1 in 5 are assaulted) is what made NIJ state what it did above.

To sum up: saying there are weaknesses with the study is not the same as saying that the conclusion that 1 in 5 women are assaulted in college is wrong (or absurd as you put it).