@Rhiannon So, I read over this one more closely. I do have some notes, to which I will get to soon, but I wanted first to point out that everything from the tag forward is spot-on.
I have but one issue. In moving the eclipse montage to join it more closely to the Hildorien shot, it somewhat exacerbates the issue of the episode timeline. We see the eclipse end (which I presume is so that when Sauron and Thuringwethil are talking, it isn't still supposed to be in effect), but then go back to during the eclipse for the montage. The eclipse ends once more during the montage, then we return to it (I realize this is a location jump rather than a time jump, but the audience may not pick up on that).
Returning the montage to its original place solves that issue (Bombadil can still be the end of the sequence). Have the sun start to peak out for Bombadil. When we do the scene with Morgoth, he is "returning" the sun to the Men of Hildorien, so the eclipse will be closer to its end.
Will someone still be on YouTube pointing out the inconsistency of Thuringwethil making it back to Angband in the minutes it takes an eclipse to end, sure. But as you say, it is a different location, and of course no one really knows how an eclipse would work in a flat earth anyway. Ultimately, I'd rather make certain that we don't jar most viewers with what appears to be multiple jumps back in time.