Well as far as quitting the job is concerned, you can pretty much leave without any consequence, you are employed illegally.

I'd even suggest that the Chinese will have far more of struggle trying to get money from you than you will have trying to get out. There's only one thing that you need to do - not hand over a single penny.

I'd suggest getting a business visa from somewhere else or if you are really desperate, just sign up to study Chinese and get a student visa until you get the business visa from a business involved with anything that you do, such as a supplier.