I really would like to see answers to the four questions at the end. Though I would hazard a guess that the answers to the first three can be summed up as "it's easier and cheaper to let China do the dirty work." The last question I cant answer as I don't understand boom-bust mining cycles.
Edit to add:
> After all, it turns out tungsten actually isn't hard to find! It's all over the United States. In fact, it's pretty much all over the world.
The Wikipedia Tungsten article states the largest reserves are in China followed by Canada, Russia, Vietnam and Bolivia. This contradicts the articles claim. Just because it's all over does not mean it is easy to dig up and refine. Some clarification is needed. https://en.wikipedia.org/wiki/Tungsten#Production
> China has 50 years of ore refinement development behind them.
No it doesn't (at best its about 35 years) and it often (mostly) uses equipment made in the west. In fact, if you want to extract something from the earth, its very likely you need a US firm to help you do it (depends on how hard the material is to extract).
> and ecological collapse
You can do mining responsibly, it just costs more. US firms about 20 years ago tried to get the US government to subsidize their industries to compensate for the extra costs. The politicians said no and voiced environmental concerns. So those materials started coming from China and the 3rd world where they were extracted using even dirtier methods than the US was using at the time. It turns out that pollution doesn't obey international borders though.
Finally, most of the material China exports is raw and its refined somewhere else. The only things China refines for themselves are either a) is easy and they need them domestically or b) the refining process is very dirty. Additionally, mining almost always takes place far from population centers. The basic reason for this is that all the material near population centers was extracted far in the past. Your entire take has little to no resemblance with reality.
It's amazing how many people think China bootstrapped its industry from first principals when all it did was lure western companies to move their production over and "learned" by copying.