I think you should at least give the law suit a try, or you will feel bad for a long time.
Don't focus on the performance issue for the law suit. Your were not let go for that reason and you will not win if you use that for your law suit. Instead, focus on issues such as "DISCRIMINATION" "ABUSE" etc. If you are the only chinese in your group and your boss is a white, you will make a strong case. Because even your performance are good but he yelled at you and gave you hard time. It can be proved by your co-workers and your previous managers.
Don't worry about the long procedure for the law suit, if the company knows it has fault, it will settle with you. You don't have to go to court and spend a lot of time.
Good luck
