I would like to propose a new theory about why the Anunnaki needed the gold. There were multiple reasons, such as using it as a super-efficient electrical conductor and for making solar cells as just two of them, but there were two major reasons.
One of these major reasons indeed was for making repairs--but, not to repair the planet Nibiru's atmosphere by suspending gold flakes Goldschlager-like in the planet's atmosphere (I frankly find the science behind that quite dubious and always have). It was, instead, needed to repair the hulls of the Traveling Star Habitat in which the Anameabi (my Sumerian-derived name for the "gods"--that is, the "ones invoked" or the "ones sacrficed to"--before they become the "Anunnaki" or "Those Who From Heaven to Earth Came") came to Earth from Nibiru in accord with your (I believe) sound theory that Nibiru actually never crosses into the Solar System proper. This Traveling Star Habitat, akin to a Starship but more like an utterly gigantic space-faring city (the "Island in the Sky" that some Native Americans say in their legends were the gods' original homes) is what the Egyptians called by the untranslatable name of Sunt, which (as Sitchin says in The Stairway to Heaven) "crosses the sky nine times per night". Just as the original planet Marduk (the true "Nemesis"?) became conflated with Nibiru, and Nibiru with the Home World in your theory, so I say that further conflation happened where the Traveling Star Habitat became conflated with all of those, too. So the "atmosphere" that was being repaired with gold by the Anunnaki was not that of Nibiru but the artificial one of the Habitat.
I have ample scientific evidence that we human beings are not responsibile for the changing weather nor for the "global warming" anyway. Sitchin clearly is interpreting ancient texts; as you point out at your website, back in 1975-1976 there were no fears of global warming, but in fact fears of the equal opposite. But he then puts the "repair our self-damaged planetary atmosphere" spin on things into the LBOE nearly thirty years later.
The second major reason was for their own youthful longevity, Jedi-like mental powers, and "immortality"-- the alchemical process of changing the gold into a substance that could be digested as an elixir (and also, perhaps, put on as a cream to make the skin "perfect" and
At any rate, I hope this makes some sense to you.