Mom has bipolar disease and depression and has recently been diagnosed with dementia. Dad took early retirement to care for her, and for the past ten years he's had to almost isolate her (and himself) just to keep her stable.
A few months ago Mom had a really bad episode, called the police on Dad, and made a lot of unjustified accusations. It took months to clear that up, and I think it hurt Dad emotionally. She's been in a rehabilitation center for the past two months due to a bad fall that broke her collarbone and shoulder (she was trying to "escape" and fell down their condo stairs).
She's scheduled for release at the end of the month, but Dad says he just can't go back to caring for her. He says she's not safe at home no matter how hard he tries, but I think it's more that he's just worn out.
My sisters say that it's his responsibility to care for her and that they couldn't bear to see Mom "in a home" -- but they're not willing to take her in. I say the man has done all he can and should do and deserves a decent life.
How do I get my sisters to see that Mom needs more care and supervision than Dad (or any of us) can give?
I wouldn't focus on trying to convince your sisters of anything. Spend your energy and support helping both your parents through this difficult caregiving transition.
Your sisters have a rather sentimental view of marriage and are holding onto that "till death do us part" line without considering that there are many ways to love, care, and nurture a marriage -- under the same roof or not -- and that it may not be safe or wise for your mother to live at home. I'm sure your dad would rather your mom be healthy and happy, at home with him and safe, but that's just not reality right now. So give him the support he needs to make some tough choices.
It sounds as if your mom's care has escalated beyond what one person can manage, and it takes a mature person to be honest and face the fact that her care needs have changed. Tell your dad again and again what a loving, supportive husband he's been and that it's OK to begin to accept help. Many care facilities, community centers, and churches offer support groups. It would be great if he could visit one and see that he's not the only spouse having to deal with this issue.
Help him find a place where your mom can stay that's safe and meets most of her care needs. Know that she might be unhappy at first. Also, know that your sisters may balk -- but this isn't about them, so try your best not to get sucked into a conversation about "what Dad should do." Just be matter of fact with them and explain that your mom's care and your dad's ability to provide that care have reached a crisis of sorts, that things need to change, and that your dad (with the aid of your mom's doctors and care team) are figuring out the best situation for her.
Which leads me to her care team -- does your dad have a support system? He needs to rally all her various care providers so that everyone is on the same page. He may need a geriatric care manager or someone who can advise him on what care facility is best for your mom. It's important that it be nearby but also that it provide the type of care her condition warrants. Even though you may have to pay for this type of assessment up front, it will cost you less in the long run if you don't have to move her time and again because a given facility isn't a good fit.
Your dad's going to doubt himself at times, so support him through these changes. Help him adjust and find new ways to continue to love and care for his wife even though she's living somewhere else. Encourage all your family members to be visible presences at your mom's care home, to set aside how they feel about it, and just be there for her. People who have regular visitors receive better care.
Then help your dad get back out into the world again. Address his health needs, since many caregivers neglect their own care. Perhaps he can join a walking or photography club, or go to the local senior center for classes, activities, and the chance to make new friends.
It's a big change for everyone, so expect a few hiccups along the way. Just try to be there for your parents, since they're affected the most. And know that you and your sisters are going to display all kinds of emotions about the situation. It's a type of grieving process, so be patient and use heaps of humor and hugs to help everyone adjust.