This is apparently going to be a big one - I may have to find another home for it. Unfortunately, it lost its leader (before I bought it) but the growth seems upright so it should pretty seamlessly replace it.
That should recover fully. Plant it somewhere with a reliable water supply, it is very sensitive to summer drought. It isn't likely to get too huge, the tallest over this way (in Ireland) is 21m tall, and most of the rest are quite a bit shorter than that. I guess it probably needs a Taiwanese summer monsoon soaking to get to a good size.
Thank you Michael. The only information I could find on the internet was about its growth in the wild, hence my concern. Twenty-one metres is still a good size though...!
Two main immediate issues are that it looks potbound (in that small pot, it must be) and nutrient (probably N) deficient. Open up roots when planting, fertilize afterward (fall is the best time to fertilize hardy plants).