Do you know what basis he has to apply for a green card? What is his status in the US today? He cannot marry in the US unless he first divorces you. As far as alimony is concerned, that is a matter of family law and you should ask a family lawyer that question. But, I am confident that the fact that you are Taiwanese would not preclude you from receiving alimony.
I am very sorry to hear about your situation. I would recommend that you speak to a family lawyer now before he takes any action.
Unless he has an employment (or other type of) sponsor ... he can't get a greencard without you signing papers of sponsorship.
PROFESSOR OF IMMIGRATION LAW for over 10 years -- This blog posting is offered for informational purposes only. It does not constitute an attorney-client relationship. Also, keep in mind that this is an INTERNET BLOG. You should not rely on anything you read here to make decisions which impact on your life. Meet with an attorney, via Skype, or in person, to obtain competent personal and professional guidance.
If he is married to you he cannot validly get married in America, or at least the marriage would be void. If his new wife petition for him while he is still married to you, that petition would also be meritless, since it's based on a void relationship. You should consult with a family lawyer to discuss the possibility of getting alimony and/or child support.