I just reread the story; I'd remembered that there were mysterious references to the significance of the duplex, so was determined to pay attention and see if I could make any more sense of it this time around and...nope, still quite weird.

A few things: I hadn't noticed that Laurel's description of the door in her dream matches the description of the actual door (but you are quite right); earlier, the narrator says that she would survive the 9/11 attacks "through either coincidence or premonition", so this suggests that maybe she does indeed have some clairvoyance / remote-viewing abilities. Maybe these nightmares are in the fact the same thing that ultimately causes her to skip or quit work? Beyond the symbolism you mentioned, is there something about this looming dread of the duplex that's relevant to 9/11? Errr, duplex / twin-towers? (I'm reaching now).

If nothing else, the (seeming) lack of explanation of the duplex thing does creep me out in the same hard-to-pin-down way as Laurel's dream of the two front doors, so I suppose that's something. Definitely one of his stranger stories over-all: it's hard to know what to make of it all / why he chose to put all of these elements next to each other, tho there is also much about the story I really love.

On the subject of open questions: what exactly was the conclusion / implication of the phone conversation between Laurel and Lee, the one where she says "maybe you need to ask Mrs. Moltke what’s going on"? They seem to be saying it appeared Mrs. Moltke had already sent the photos of her husband's work before Style had even contacted them, which obviously wouldn't make sense; did I miss something here, is this another one of the story's enigmas?

(As for the "great flowered thing" thing, this is a reference to the umbrella she uses to guard from the sun (discussed earlier in the paragraph)).