How can i escape liability from abetment to suicide

My bf is threathening to commit suicide if I don't marry him. I know I asked him to marry me in the first place but now I don't want to marry him. He is too possessive and keeps on doubting me if I refuse getting physical with him. I don't want to continue this relation anymore. He gets abusive n aggressive. Before he had hacked into my emails and fb account and used to blackmail me by saying he would tell my mom about all my previous relationships. He also have taken my documents and few other things on different pretexts but had never returned them. Few he did after I pleaded with him. He still have my things.I am too depressed with all this. N want to break up. But he doesn't allows me to . Now he wants me to meet him n take back my belongings but m sure its just an excuse to meet me he will again talk in such a way that I won't have any option but to obey him. I do not want to be with him any longer and neither can I inform anyone about the situation as my mom who is a widow won't be able to take all this. He knows veery well I won't involve my family and hence he is taking advantage of the situation. Kindly advice as what can I do .