Daas,
Chas V’shalom, I never “conceded” anything. I have maintained since the beginning that there are two separate dinim: (1) that a married woman must cover her head having nothing to do with erva, and (2) that if and when hair is normally covered it gets the status of erva.
R’Moshe cannot make up issurim d’oraisa, there has to be another source for it according to your reading (You can’t make a kal v’chomer unless you have some other din in which it is already more chomur). According to my reading R’Moshe is NOT saying that basar is d’oraisa. He is saying that basar is has a greater status of erva than hair and can therefore be erva, with respect to krias shema (he is not discussing walking around in public, which is a SEPARATE DIN), even if it not normally covered.
You are only understanding R’Moshe they way you are because you are trying to understand the Gemara in Kesubos as erva based. There is no discussion of erva in that Gemara, there is no questions from the Gemara in Berachos.
Rashi s.v. “v’derech mavui” says “that the public are not common there.” Neither Rashi nor the Gemara mentions men in connection with covering hair. There is no indication that it has anything to with men (in her home it is mashma it would be mutar even if there was a man or two around). The issue is public versus private. Similar to the way that a Rav or a Rosh Yeshivah won’t go out of his house without a hat and jacket on, but will meet people in his house without them.