Your situation sucks in many levels , I’m sorry
I am glad you have a month to month lease and her sister did agree to a much lower rent each month thankfully.
My daughter also just due to the unbelievable rent where she lives also rents a room, most have all worked out well luckily. She got in one situation kind of like yours. My daughter has Bipolar so finding out a roommate has undisclosed mental illness wasn’t a huge problem , but shes never felt unsafe so there is a difference of course. My daughter did buy a small dorm size refrigerator for her room so her food wasn’t being eaten.
As for taking care of her son? No just no.. if she yells for you to feed him or drive him, you simply say no.
Why not ask her sister to have a lock installed on your bedroom door. Would give you more of a sense of safety maybe?
It’s true unless someone is suicidal or a threat to someone there just isn’t a bed IP for them. If she doesn’t want help to get better no one can force her.
It sucks that your in a situation that right now you have no way to physically escape and find a better living situation
It is possible that her sister is using you as a safety net for her sister , if things get outta hand she probably thinks you would call her. Totally wrong for her to do this to you. Does she expect you to call her if her sister really gets bad or something?
I’m sorry your in such a lousy situation