Nice story! But I got lost in the Corbenic timeline again.
So, our Earth is 2N.
The third moon, as per 3319, is Earth 2M.
Girard Niang's earth, as said in Radical Acceptance, was the one who neutralized the Hill (also, in Radical Acceptance he describes it as if he's seen it himself but now we know that it was almost 300 years prior). It also was the first moon of Corbenic. And here we learn that it was Earth 2L.
But what about the second moon? There are no letters between L (first) and M (third).