Gatekeeper isn't serious about sending in the PLA.
I hope so.
Cutting back water supply is bad publicity.
As I said, I would simply let Hong Kong keep losing economically. Only if the island declared independence would I reduce the water supply to where showers are not possible.
Simply keeping mainland money from flowing to HK and discouraging tourists to visit HK are enough to bring HK economy down a few notches.
Yes. Expanding the harbors of Shanghai, Ningbo, and Shenzhen, thus taking even more business from Hong Kong, would also do it. (Note: these harbors are already bigger than Hong Kong.)
Although I would say if the HKPF can't keep the rioters from even more extreme violence, then the central government might have no choice because it becomes a sovereignty issue.
No, Beijing will have many choices.