I feel for you.
It may be of little consolation,but you're neither the first nor the last FT to be used and abused by a rogue Chinese recruiter.
If I were in your shoes,I'd do a runner on Friday evening after class.By doing so,the chances are your absence won't come to light until Monday morning,by which time you'll have been able to exit the country.The only way you'd have trouble at the airport would be if your employer via the foreign affairs office in Chongqing managed to contact airport customs before you had exited the country - highly unlikely if you leave China without unnecessary delay.
Good luck - you certainly deserve it!