(b) How is the GA scene in the US/Australia/NZ like? Are low hour pilot employers and flight schools willing to hire expat flight instructors? Visas are probably not going to a big problem if I do the training through aviation degrees. For Australia, I may have up to 5 years for hour building under the temporary graduate (Subclass 485) visa. (Feel free to correct me if I don't qualify for that 5 years visa using an aviation degree)
Gooday, I can't really answer most of the question but I can share some of my personal experience for you. I've trained in NZ and training here is awesome but very depends on which organization you go thru.
During my time to start is hard as aviation is blooming during 2017, good flying school is picky and they rejected lots of students, as im not the smartest student to fly, I've nearly been kick out from the school.
And getting a GA job after graduate in here is always hard and i thinks its the same as over OZ especially post COVID19.
15 of us local students maybe 3 got a aviation job, others of us = supermarket.
I met alots of Hkers came over our flying club and grab a PPL license and go back to apply cadet back in Hk. Maybe you can do that just to experience the taste of flying to see if it suits you.
All the best!