I've never felt so totally spent. What's left as options?

This isn't going to be a Readers Digest version, sorry. My Mom, who just turned 80 today, was officially diagnosed with Dem/ALZ 4 years ago, just 2 years after her being told she beat breast cancer on her 2nd bought (had a mastectomy). I probably ignored some of the signs because she retired from working a year before that and I just thought she was just trying to get used to that, probably-maybe. ALZ runs in my family (Mom's side) and this is the 5th time I've had to do this since I was 11 y/o. Just to preface, major changes; cog/phy; all happened after an afternoon nap - or as we called it , the hour of change. First time was my great uncle who lived only a block away from my grandparents and I used to go over there to help my Grandma take care of him. His wife had terminal cancer and passed within a year of diagnosis. That lasted for 4 years til his death; due to ALZ. About a year before his death, my Grandpa stated his mental decline due to Dem/ALZ with suddenly wandering outside at all hours of the night in any weather in his underwear. The next change,about a year later, was having issues with incontinence which then progressed into verbal abuse. After he started getting physical with us, we finally had no choice to put him into a nursing home. Literally, within a couple of months, I was the Only person he remembered. It devastated everyone; understandably so. He stayed like that for nearly 2 years til he passed away from complications from the Dem/ALZ in '83 when I was a senior in h.s.. A couple years later my Grandma had a heart attack and was heavily medicated for about 6 months after that and suddenly, again after her afternoon nap, she woke up and had a hard time with remembering anything. If she saw pics from 15 years before, she could remember who everyone was but the next day, we had to start all over. Again, she had no issue knowing who I was, which is a pattern I do Not understand. I had 12 years off while I was married but my job at the time caused my divorce 8+years of 21days straight-16hrs/day and on the afternoon shift. Soon after the divorce, my aunt started showing signs of Dem/ALZ by getting lost for hours going back and forth from the store. The last straw was when the P.D. from a town 15 miles away called and I had to bring my Mom with to drive her back home (that's when my Mom was going thru her first battle with breast cancer). About a year later, again after her afternoon nap, just 3 hours after taking her and my Mom shopping for clothes for an anniversary party, we pulled in and "Lucy" was balling on the porch. My aunt didn't remember her, she has been part of our family for 60 years at that time, or my Mo but again; remembered Me and was asking for Me. She said she couldn't walk, those 2 ladies; my Mom and "Lucy" hid her wheelchair and took her money. My aunt didn't have an issue walking and her money was in her drawer like always. I dealt with that til it was too much for "Lucy" and Me and she was put in a home about 3 years ago. She cannot remember anyone or anything. Now it's Mom. She constantly complains - almost Every sentence. She's up 20 hours a day and can fill up my voice mail, 125 messages, in 3 days. For the last year, if she's up I HAVE to be down there. If I'm not, she calls NON-STOP and leaves a message. From the time I go upstairs to sleep for work 3-7p, she'll call every 10-15 min and leave a message. That's on those day when I pass-out out from Not sleeping for 2-3 days straight. Yah, Maybe 3 1/2 hrs sleep/day to drive overnight for 12 hours. This has been going on for the last year and within the last 3 months has caused me to take at least 1 night off/week basically negating any O/T for the week (the policy, even with FMLA, is that once you've used up your 7 vac days and 7 sick days you lose O/T pay for that week). So for the last month I've been lucky to get 40 hours. My 2 younger brothers are no help at all. I mean, I'm 51 now, and at even at 25 I couldn't work 3-12's without sleep even with a desk job, so I have NO idea where I'm getting the energy from. There is no help from home care services since they don't do weekends. I Must have help Fri-Sat-Sun from 2p-6p since she is allotted 12hrs/week from the state but there is no service available. Both her GP and Neurologist want me to get a Fitbit and bring it in to get connected with Their monitors. When they said that, I got scared! My ex-gf, a retired psychologist, said that they think I'm going to have a heart attack or nervous breakdown. I know that I get frustrated easier now than ever before but I haven't started hitting the bottle or punching holes in walls yet. I have noticed that I don't want to do anything but sleep if she's quiet so I don't have to deal with her griping and bitching about everything for just a few hours a week. A.L.C. are out because they are $5K/mo. I just have nowhere to turn for relaxation...None. What's left as options?