Yes, that is tough stuff. My Mom's memory care facility is only about 40 people, and they have quite a big staff, so it's manageble for them. And, if she worsens -- there is a facility on the bottom floor for more help; kind of like residential care.
Residential care homes are quite nice, but just know that if your Mom is on hospice, many will not accept hospice patients. Also, go and check some of the residential care homes out and as thebrothersmother suggested, find a support group that can help you.
Your Mom might thrive better in a smaller home; I had a grandparent that was in a smaller home, and it was very nice, and she enjoyed it because they gave her more attention. Take care, and keep in touch.