As regards diagnosis, I really appreciate what you are saying about the brick wall and I think this is common. One thing some people find useful is to make an appointment to see the person's doctor themselves to discuss concerns. I have heard often doctors can then, depending on their relationship with the person, contact them for a 'general check up' but will be obviously looking for signs. Sounds a bit sneaky but sometimes a bit of sneakiness is required.

I am not sure how it is in the US but in the UK diagnosis is important for accessing services and support.

You sound like you are coming to terms with what is a pretty life changing illness for your mother, and you've had some great advice on here. You need support for yourself in order to support her, maybe you can check out carer support organisations in your area. Take care!