Feel No Guilt
At one time in your life you also were helpless and demanding, requiring 24 hour care and making your caretakers stressed beyond belief. This is what is expected of a parent. This is not what is expected of a child.
Parenting, wonderful or abusive does not come with the obligation of elder care. No parent should want their child to suffer on their behalf.
If you are able to provide care, then do so. If it is beyond your means, financial or emotional, than don't. No one is expected to sacrifice their life to care for another.
Call their doctor, clergy, social services, local nursing home, anyone..keep calling until you get the help you need. Do not feel guilt. You are of no help to them if you are unable to function.
Die in a nursing home? Do you think they won't die in your home? Angry and bitter? Perhaps at first, but you will be in a much better position to monitor their care in a facility than be overwhelmed at home.
Find someone who will listen to you vent, find something that makes you smile no matter how small.
I just lost my mother after years of care both at home and in facilities. Her decline was stressful both at home and in a home. The drain on finances and emotions is immense but survivable.
Do not allow yourself to be trapped. Do not allow yourself to be devoid of any happiness. You can salvage your life, there is help, you are not alone. Get help.