1) At this point there is the
answer to your question in the following passage:
But where Typhon falls in and touches upon her extreme parts, [...] For which reason the fable makes Typhon to be married to Nephthys, and Osiris to have accompanied with her by stealth. For the utmost and most extreme parts of matter, which they call Nephthys and the end, is mostly under the power of the destructive faculty;
(Plutarch,
De Iside et Osiride, 59)
There is no doubt that the 'air' is meant as the place of the death of Osiris by Seth.
2) I see that you are already
conceding to me this identity/similarity of construct:
κατώτερος μέρος τῆς γῆς = τῶν ἐσχάτων τῆς ὕλης
3) and so, in virtue of points 1 and 2, since there is the clear identity/similarity of construct:
''the utmost and most extreme parts of matter'' (Plutarch) == κατώτερος μέρος τῆς γῆς (Julian) == τῶν ἐσχάτων τῆς ὕλης (Ephesians)
...you have that very probably, the ''the lower, earthly regions'' are equivalent to the region of the ''air'',
the same place where Osiris was killed (
beyond any doubt).
CONCLUSION:
the author of Ephesians placed the crucifixion of Jesus in the region of ''air''.
Ergo Paul, also.
Ergo the Pillars, also.