The main idea of "The Distance from the Moon" is a complex metaphysical one bound up in the metaphorical conflict between the Earth (the physical) and the Moon (the metaphysical, the cosmic). The narrative shows there are two kinds of perception that at one time were more closely related and undivided than now and that existed then without metaphoric jealousy of each other.
Mrs. Vhd Vhd was becoming jealous of the Moon and I was jealous of my cousin.
These two perceptions, or consciousnesses, are represented by (1) the Deaf Cousin (who is not given a name in the narrative) and the Moon and by (2) Qfwfq, the story-teller and the Earth. The Deaf Cousin is deaf to Earth's interplay of relationships and emotions: he is pure perception of the larger cosmos. Qfwfq perceives only with Earth's emotions: he is blind to the cosmic greatness.
This should give you an idea of how the influences of Earth and Moon, practically equal, fought over the space between them.
When a part of Earth, in the figure of Mrs. Vhd Vhd (whose husband, Captain Vhd Vhd, does not regret her absence) becomes one with the Moon by declining to return to Earth (following the one month exile forced by the retreating distance of the Lunar orbit), Qfwfq and his dogs--sensitive to their master's psychological and emotional state of being--set up howling for what is lost from human, earthly, perception.
[Mrs. Vhd Vhd] who makes the Moon the Moon and, whenever she is full, sets the dogs to howling all night long, and me with them.
In contrast, the Deaf Cousin, who has no affinity for Earth-bound perception, rejoices in the movements of the larger cosmos and seemingly pushes the Moon into her new, more distant, orbit, not for the sake of the distance or the newness, but for the sake of the cosmic reality that he, being deaf to Earth's perceptions, can fully comprehend. These cosmic perceptions are what Qfwfq cannot even glimpse.
you would have said he was driving the Moon away, that he was helping her departure, that he wanted to show her to her more distant orbit. And this, too, was just like him: he was unable to conceive desires that went against the Moon’s nature,...
Thus the main idea is revealed as this: Life on Earth combines the larger metaphysical cosmic perception with the narrower Earth-bound emotional and psychological perceptions, though some may perceive only one or the other and may be unable to perceive both at once. Yet, all now have the option to perceive both since the Earth-being Mrs. Vhd Vhd is one with the cosmos and can potentially serve as the bamboo bridge from one consciousness to the next.
the more it waxes, the more clearly I imagine I can see her, her or something of her, but only her, in a hundred, a thousand different vistas, she who makes the Moon the Moon...