My question involves real estate located in the State of: Massachusetts

My mom and stepdad owned a house - mom passed away and stepdad has health issues / mental health issues. We did a Quit Claim deed granting the house to me with a life estate stating that he had the right to live in the basement apartment for the rest of his natural life. I live upstairs, where I have lived for over 10 years. We have always split the mortgage, without a written agreement... He insists that with the life estate, he does not have to pay any of the mortgage, that I am responsible for the entire monthly payment - even though the mortgage is still in his name.

First off - who is responsible for paying the mortgage payment?

Second - can I just walk away since he is still alive and I no longer want to have anything to do with him, nevermind live upstairs from him... He is manic depressive and has been acting up recently (again), breaking into my apartment, physically assaulting me and verbally trashing myself and my son. He was involuntarily committed to a mental institution a couple weeks ago because his POA and Health Care Proxy feared for her safety and the safety of her family. He has been released and is now back in the house.

Any advice would be greatly appreciated.