What do you do with a Mother-in-law who tries to destroy you?

I am a 27 year old female who is on the brink of a breakdown. My mother-in-law just about got me killed. I used to be a police officer in a little town, she gave very personal information about me and my family to a known "psycho" who then was caught writing "Kill ...my last name" on the back of my pickup. She has destroyed every job I have had since I moved with her son to this god awful state of WV... My husband has a child of his own and when ever my step-son comes to visit she constantly reminds me that I am not his mother....she even called the biological mother and told her I was abusing her son and they even made fun of my battle with cancer (the reason why I can not have kids) the worst part about this is that my husband will not do anything about it, he did prevent her from coming to our home, but he laughs at the matter. I am afraid to apply for any more jobs due to her history of slander and defamation of character. WHAT DO I DO? Desperate in West Virginia.