Just sending you lots of hugs. Speak with your mom's oncologist about hospice care, and other medical questions you might have. I can not answer most of your questions but I can tell you what my family did when my parents were in the final weeks of their lives. It helped comfort all of us during this phase, and we realized that it also helped us in months and years afterwards - it's been 6 years for my mom and almost 3 for dad.
we visited them a lot and told them how much we loved them. We let them know that it was ok to let go, of their suffering we would understand. We kept them as comfortable and pain free as possible. When your mom has the energy try to do something low key that she enjoys. I still remember my then 16 year old daughter reading to my mom and my nephew playing their guitars in my father's hospital room. Reminisce about the fun times you had.