Should I quit my high paying, 20 yr career job to take care of my Mom who has Alzheimer's?

My Mom is married to a nice well paid guy she's bossed around her whole life, but he loves her anyway. They've had alot of fun together, she's been the creative energy in their relationship. Now she's regressing and acting like a brat, spending money she doesn't have. He never was the "boss" and he's having trouble controlling her terrible behavior now. She shouldn't be driving anymore but he doesn't have the heart to take away her car..in spite of the fact she will soon be a menace on the road. We've known this fate has been coming for years, her mother, my grandmother, also passed from this horrible disease. It will probably be my fate as well as my two sister's fate as well. I live halfway across the country and have a chronic condition that would keep me from being able to get private health insurance so I need to hang onto my job. BUT my Mom and her husband (not my Dad) are in denial about her condition. She actual found a quack Dr. to tell her she was just fine, though she has no concept of numbers, money and has lost her ability to read in the last couple months. I'm almost 50, my Mom is 68 and her husband is the same age. My youngest sister who stayed closest to home is trying to keep them afloat and currently, she can do this b/c she's married and supported by her husband BUT she would appreciate the help. I'm posting this in the "GLBT" section b/c most "ya'll are my ppl". I don't expect any one person to have a clear answer here but thanks for letting me talk...and I appreciate any feedback. Thanks for commenting. 'Sad for Mom in Minnesota'