Having now read the original 1951 version and glanced through the 1986 version: (There are many more versions between; however the 1986 version is the first I know of that contained the entire uncut story.)
Kalki shows up in the version that was revised just prior Heinlein's death and coincidentally after Indian astronomers theorized a tenth planet that they named Kalki after their tenth avatar and my guess is that someone else added this to his work since he claimed earlier in his career that he had learned his lesson about changing certain scientific datum in his work to reflect present times. (But I won't entirely rule it out.)
The B. W. boys is likely a biological warfare reference to the parasites. Since he seems to include forest fires with epidemics and later when talking about virus and plagues as weapons against them in biological war and warfare.
There are some interesting things to note in the difference between the two.
There are references to other works
In both books there's a reference to Charles Dickens' David Copperfield, however the reference to Frank Baum's Oz is not in the 1951 version.
More importantly there are several references to description of Mary that have been alter shortened or cut completely from the 1951 version.
One of the largest of these is from the scene in his cabin in the woods where they are first intimate. All through both versions we see Mary as being overloaded with all sorts of weapons. However the scene missing from the 1951 version contains evidence of some validation of her qualifications to use them. I think that the missing scenes and piece are all integral in having a clearer understanding of Sam's true assessment of her as a viable partner and the original is somewhat weakened by the exclusion.
There is also some subtext to the place where the old man tells Sam that Mary is a much braver person than Sam is; and it parallels a short story Heinlein wrote
NO BANDS PLAYING, NO FLAGS FLYING
that was based on a true occurrence he had witnessed.
I think that the later version has a much better handle on Mary's character.
Also the entire sentence talking about B. W. Boys is not included in the 1951 version. I had to look back to verify that.