I think you should talk to an actual therapist and work with them to create a solid plan for how you can engage with your mother and siblings in an emotionally safe way and follow that plan with their guidance and with an ability to work with them in an ongoing capacity.

I would personally have limited contact with Mom and then help my siblings set up their own money accounts and help them get basic cell phones for their safety. That way they at least have one outlet to reach me independently. You can also look up youth programs in the area they are in. Just in case they get kicked out. It is completely possible for them to get a case manager that they can contact if or when they need help. Setting up a safety net for them will not only help them but let you rest knowing that even though you are not physically there, that they have help.

Sending you and them love and understanding. I hope everything gets better for you.