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>  have lost my count at how many times I have been dreaming about this

Have you looked up any dream dictionaries? They're fun, sometimes useful, sometimes frustrating, and often a new-age barrel of crap.
The reason "dream dictionaries" work, is that the human experience transcends cultures and times. Except where it doesn't.
The trick I've latched onto in interpreting dreams, is that everything there, is you. When your uncle shows up in the dream, it's not your uncle, it's how you feel about your uncle that shows up in the dream.
Usually I've found that if you read several common reasons for a symbol, such as water, to be used in a dream, that it will "feel right" and you'll be able to piece together what the whole of it was.
And in my case, they're usually elaborate questions, like the mice building Earth in Hitchhiker's Guide
Other times it's a frustrating mess because you know this aspect means something, but you can't find what.

> Since you live in Europe, you may not relate to this at all, but it occurred to me after I wrote down the themes and the one recent example. In the cave-city, all the streets were in shops and the like, and they were stuff to overflowing with ... random things.
are you referring to  enclosed streets that work like a shopping center or a huge market but full of little stands?. I live in Europe and I believe that Madrid has one of those, so I perfectly know what you mean with this.

> The feeling I had in the dream was very memorable, and one I've felt before. But I don't know if you'll understand if you've never moved into a stick-built standalone house that someone else just moved out of.
I haven´t moved out so far and the stick built houses are not all that common here. My smalltown does have a few ones though (we call it the American houses) but the rest are either housing blocks, brick or modular houses. 

> Did you ever move in, and find their junk drawer still full? The first of two houses I lived in during my childhood, we were renting a house on the water, and there was a barn that had been used as a shop, a garage, and a storage area. It was still full of many, many metal items. Both small parts, and complete ... things.
despite not moving into this kind of houses, things are starting to make sense.

> I understood I wasn't supposed to mess with them, but the sheer wonder at their intricacy that spoke to some alien design and applicability to a purpose.
any child would be curious and mess around with them in a mindless manner during the first day. However...

> To say I was mesmerized would be a great exageration, but I was certainly filled with wonder. And I have felt it every time I moved -- looking for that, which was left behind, and trying to piece together the stories they tell.
not many kids would spend their time at figuring out the secrets behind them later on. I don´t remember many things from my childhood very well (especially the period of the 5 five years of my existence) but considering that you are attempting to find those answers to this day, maybe you are saying doesn´t sound all that exaggerated because many other kids would have forgotten about it the following day.

> Why does my subconscious include that feeling in a story about accepting a job from a muckety-muck who wants to have another factory running for his profit?
because of the brain connections with what you were mesmerized. If that feeling of wonder becomes recurrent and stuck inside your head, there is a great chance that you mind will connect that into something completely unrelated within your dreams. One can perfectly dream about MLP and then, arise out of nowhere a divorce that one witnessed about its cousins a few years ago and mix them as if those things were naturally  related.