As far as the analysis of the "two names" that have always described number five, I often think those were simply "number" and "five"; (in other words, I think the narrator has the name Wolfe, but that the particular statement of having two names might be irrelevant to it; or at least not a "specific" clue [of course, it isn't much of a clue with our common naming conventions removed from a patronymic system]) but nice point about the attendance roster alphabet. Perhaps the role is arbitrary... certainly his last name starts with a W from those library clues... it must be Wolfe.
By the way, you mention pictures of Wolfe ... in Letters Home, there are some surprising pictures of him. For one, he is RAIL, STRING BEAN POLE thin. I am not kidding. He was really skinny as a young man, with a kind of narrow face but prominent nose. He doesn't resemble those pictures in the least now. Indeed, he boxed in the military at about 135 pounds (I'm not sure how tall he is, but he looks to be of slightly above average height in the photo; certainly tall for 135) (I'm 5'8'', 125 ... and he looks narrower in the chest than me in those photos).
I've read Fifth Head, but I'm not super-familiar with it; my convictions about the text are tenuous and should not be taken very seriously. Marc Aramini