Go to counseling to understand what has happened--even if you know why a break-up is pending, maybe she needs to look at the rigid line of JW married life. See it through another person's perspective.
But I would leave if there is no emotion, passion for life that you share.
You are good to be thinking of her welfare--but she is stuck in an impoverished world in more ways than one. Perhaps offer her financial help if she will get training to better her income-earning capacities. Sisters I knew had their backs and knees wear out from housecleaning jobs.
sorry about your brother. I'm glad you got to be around him more these past years.