Dust,
I'm sorry for your loss but like others, I don't believe you can legally prove out the extent to which your mom died "prematurely." However, it's a valuable example of something we talk about here, that hospice, if any, should be a conscious choice, with interviews and perhaps references behind it, that they can/do want to have their own staff/procedures, that there has to be oversight because ALS is so rare and care should be individualized to the patient, not the disease. And P/CALS have the right to dismiss any/all staff from the home, at any time, for any reason. I'm not second-guessing what you did or didn't do, Dust.
I wish you peace in coming to terms with your loss, and encourage you to share your concern with your mom's clinic, the local MDA/ALSA, and so on. You might also write a letter to the hospice CEO asking for an investigation and report back to you, with a copy to all those same groups. While not the same as legal action, it will put management on notice and help protect future patients. If your mom was on Medicare and/or Medicaid, I would copy the local ombudsman and QIO (quality improvement organization, listed by region on line) as well, and/or the case manager of any private plan.
All the best.
--Laurie