If your CEO is a genuine prick, there's nothing I can say here that can help you guard yourself against his decisions.
You are correct, its a buse of cheap labor. He knows the my soul is in his hands to renew my work permit, that's why he is doing that to me.
If your manager is an average manager, he will know once you put effort into your job, and he will tell his superior when there's a problem. I say you try not to worry so much about it (I know it's easier said than done, too!), and keep doing the best you can.
I don't think a good person will fire you if you try your best.