I don't know the answer to your last question and probably your doc doesn't either--mine refuses to give me 'numbers' as he says they are so often wrong.
I can well understnad your mom not wanting any further treatment which will make her feel bad and give her less quality of life.
Hospice should sort out her pain meds etc. and everything needed to keep her comfortable.
From a personal point of view, I would say the best thing you can do to make remaining life the best for her is to ask her what she wants to do. And if it's in your power, arrange it.
I went to California to see my daughter in November--it shattered me, but was well worth it.
My partner and friend made sure the house looked nice for my son to come for New Year.
My chemo did give me more time, with relatively few side effects, but if your mom is in pain, then I think control of that is the most important thing.
And I would get out all the family photos, go through them with her and talk about happy times.
Just my thoughts,
Brenda