How do you cope when there’s big stuff to do and no one to share the load?

(Sorry, this will be a little long.)

I am in my 60’s, still working FT with no plans to retire from a job that I love. I am the sole caretaker for my mother, who sold her house in another state & came to live with me in 2013. I am her general & healthcare POA, but we haven't needed to use them yet. I am single (divorced), and most members of my relatively small extended family live at least 1000 miles away. Everything went well for 4+ years. I have some flexibility in my job so could help my mother settle in. She got to know some new people; she enjoyed cards; the occasional concert, play, or movie; and we had a few visits from – & trips to see – friends & family. I know how fortunate I am to have an amazing mother & an amazing job, but I’m wrestling with a couple issues right now and would appreciate your thoughts & suggestions. 

First, my mother thinks it is time to move to AL; earlier this year she asked me to collect information about several facilities. (I told you she’s amazing!) Then she fell early this summer, fracturing a couple vertebrae & a rib. She did two weeks in rehab & made good progress at home for about 6-8 weeks, but in the last month or so things have changed. She’s sleeping more, losing weight, having trouble remembering things sometimes, getting confused & then frustrated with herself. She sometimes refers to herself as “very ill,” and says she knows she is dying and is ready & not afraid. Vitals are all fine, she has no chronic illnesses, is still mobile & lucid, but she’s just sort of weakening & fading away. So I’m realizing that I need to rearrange my work schedule this fall so I can help her find and transition to a good AL facility. She is willing to look at a couple places nearby, but is most interested in a place in the town where she used to live, which is about 400 miles away.

Second, I don’t know how to talk to my sister about any of this. She’s my only sibling, & was the subject of my first question on this forum. She has a lot of physical, emotional, and financial problems that cause her great suffering and fear, but she turns her unhappiness on her family. I’m the primary target right now; my mother sometimes runs a close second, followed by her (adult) kids and miscellaneous other people depending on what’s bothering her at the moment. I know my sister loves our mother, but she sees everything through the lens of her own feelings, and she is totally unable to control those feelings. Whatever causes her anger, fear, grief, whatever – all of it is someone else’s fault, and she unloads on her chosen target with demands, then accusations, then curses, tears, & screaming. It's exciting. :-) 

I know what I need to do: free up my work schedule for a few months, make plans with & for my mother, implement those plans, and keep my sister in the loop while maintaining my boundaries with her. I’m just not sure how to do this without the personal satisfaction & uplift that I get from my job, and without the emotional & moral support of a spouse or sibling. It’s hard to navigate this stuff alone, so tell me: How do you organize, cope, &/or maintain your sanity & sense of humor when there’s big stuff to do and no one to share the load?