I am 63 and my sister 65 and both of us now share the care of our 90 year old mother with severe dementia. Any tips?

My father died 10 years ago and since then I have been living with and caring for my mother. First 7 years I pretty much did it alone and it was manageable because she didn't have but a touch of dementia (very minor forgetfulness) ....but was always fearful of being alone and I had to take her everywhere I went. I could no longer hold a job because of this so I decided to try to make it work off my retirement savings and the small amount she gets from SSI.

Last three years my sister has done her equal share since she stopped working.
Now our mother is 90 with severe dementia. The money is running out.
Our mother doesn't want to shower, refuses to be alone even for a minute, follows us around the house, has extreme fear of being alone.... at times has bursts of aggression and anger that scare us.
I am 63 and my sister 65. All other family members refuse to help us. Both of us are now into our last chapter of life and both of us have several health issues ourselves.
Being with our mother is like being in a prison. When my turn comes up I live alone with mother, but luckily my sister has other people in her house that give her a small break.
I especially am at a point where I no longer have the strength to endure this but we cannot put our mother in a clean , well maintained nursing home because we simply don't have the funds to do so. The nursing homes that we might possibly be able to afford are run down hell holes that we would never, ever consider putting our mother into.
Only thing that helps me is phone calls with friends.
I know no one can really help us, so I guess I'm just looking for messages of support to make me feel better. The severe stress is taking it's toll on my health and even at 63 I feel I'm too young to die and want to enjoy some life still.
Let me know if you have a similar situation and maybe give me tips on how you handle the isolation , sadness, and severe stress of living with someone who has severe dementia.
Thank you