Talking about reality is so cool.
Did you lose your job to some engineer in India? Were you in software?

About teaching calculus in English in a Chinese school, you will have to
find a very very good school, and better with a translator.

Math in pure English to Western students is clear.
Math in pure Mandarin to Chinese students is plain.

While I have been teaching:
Math in Mandarin to Western students who are learning chinese.
Math in English to Chinese students who are learning english

In both cases, they are curious and show great interest, but confusion
rises from time to time, the gaping eyes, ..., you will have to explain
it in their native language ...

Yes, I speak & write fluent English, but going to an American teachers'
college for a degree, what's the cost? How long will it take?
6 - 12 months in the West will be enough for me, definitely not
interested in a citizenship.

I know I have no chance for experience in a public western school.
Even a private western school, the chance for me is slim, slimmer than
your chance of Calculus in English in China, right?