Seeking Guidance When Parents Are Extremely Abusive - As-salamu alaykum

As-salamu alaykum. I have a friend at university whose family life is really difficult. His mother is never satisfied and becomes very harsh with her children when things don’t go her way. She can be verbally abusive and even violent sometimes, and she uses guilt and hurtful comments to control everyone, including the younger kids. His older brother finished his studies, got a decent job, and is supporting the family by renting a house for himself, his siblings, and their mother. He saved to buy a home to secure their future, but the mother dislikes the neighborhood and insists on a “better” area. She wants him to rent somewhere else or take a loan that would involve riba (interest) and put him in debt. Living in a place where loans are common makes it harder, but the brother strongly prefers to own rather than stay in unstable rented housing. When he refused, the mother reacted very badly - rude, abrupt, and physically aggressive - and he had to leave the house that time. They consulted an imam or scholar, and while they received relevant Qur’an and Hadith, no concrete help followed. I suggested that if the abuse happens again they should consider calling the authorities and opening a legal case so a court can assess what’s best and protect the children. In some cases professionals may recommend mental health support for the parent, which could keep the family safe. My worries are she may force them into sinful financial choices for her own benefit, or the situation could escalate and harm the family spiritually and physically. Please don’t suggest going to relatives - we tried that and they just make excuses for her, mention her difficult past, or quote scripture without taking action. Many communities mean well but don’t help in serious cases, and then judge those who seek other solutions. I’m asking for practical, faith-based advice: what steps can they take to protect the younger siblings and avoid falling into sin, while still fulfilling the obligation to be respectful to parents where possible? What rights and options do Muslim children have when a parent becomes abusive and forces them toward interest or other harms?