Hi Taylor,
As I understand it, the issue is you dont live at home. Can’t you move back home? Maybe spending a night at a friends near university occasionally, but still residing at home?
Or, thinking outside of the box, have you looked at the Open University Law degree course? You could study from home and could care for your mum at the same time, without leaving the house. Therefore, as you aren’t driving to University, Motability shouldn’t have an issue!
Stuart