Divorce and custody of my child?

Can someone pls give me advice on this urgent matter? I be filing for divorce with my wife, she is a vietnamese holding a long term visit p, not yet a PR, we just cant get along and we both agreed to divorce after too much dispute and it affects my family life n work. We are married close to 1 year only sad to say. But we be fighting for the custody of my 5 mth old daughter, do i stand a better chance or will she? She already threaten to kill my daughter n herself if she cant get custody of my daughter. And how much alimony will i have to pay her roughly? Need someone to render help and advise on this matter. thanks!!