What a difficult way to live. I understand why you are so frustrated. I do agree with you that it would be a mistake to go back to your husband. You deserve better. Believe it or not, I also agree with your father. Trying to change your mother is futile. Why put yourself through the frustration that comes with trying?
You are not going to change your mother. You are not going to change your sister. What you can change is how you deal with the situation until you can get out.
There is no point in defending yourself or arguing. Arguing with your mother just tells her there is something to argue about. When a rational person argues with a crazy person, the rational person ends up looking crazy, too. If your mother invites you to fights, decline the invitation. Say something neutral (like “I’m sorry you feel that way.”) and leave. If she blocks you when you try to leave, just stand there and hum, pray, meditate — whatever helps you not respond — until she gives up.
Your daughter has it right. Lock up what you don’t want your mother to see. Stay in your camper or visit friends or the library or go for a walk when you’re not at work. There’s really no reason to go over to her house. If you help out, she criticizes. If you don’t help, she criticizes. So why put in the effort to help?
Meanwhile, make a plan for how to get out of there. Can you get a better paying job? Would it be wise to get some schooling to retool? Can you do some volunteer work that will prepare you for better work? (At the least, it will keep you out of your mother’s crosshairs.) Is there live-in work in your area (like being a nanny or caregiver) that you can consider?
Do team up with your daughters on all this. They are old enough to be a team with you. They don’t need to argue with your mother either. It won’t change her. It only depletes them. Work together to figure out how you can make a better situation for yourselves.
I also suggest that you and your daughters find a family therapist to help you sort out how best to manage living on your parents’ property until you can get out. No, I don’t think you are “crazy”. I do think the situation is crazy-making. You deserve to have someone in your corner who can potentially come up with solutions you haven’t thought about already and who can provide you with some support.
I wish you well.