Woah, I read the whole story and I am really astonished. I would be in huge panic if I were in your place. Never trust these Chinese people.
I guess you have all the required prrofs you need to file a complaint against the exchange. I would suggest that send the screenshots to the exchange and tell them that you will file a complaint against them.
This should fear them and they might return the balance to your account. Do this and wait for a response and if nothing works out then you should definitely file a complaint.