100% agree.
Your mother was an adult and you were a child.
Your childhood sounds horrific and your mother continues with her denial by wanting you to move on.
I think you really need to spend money on the best therapist you can find.
You need to look at finally putting YOU first and consider going no contact or very very low contact with them.
How awful that they are living nearby.
The good news is that they have money and can spend what they have on getting help.
Do not get involved in their care.
Be wary of being involved with your mother, she has used you as her crutch all your life and you do not owe her your future.
Reading your OP reminds me once again of just how much I admire beyond words the women who up and leave and go to a refuge, often with nothing, just to get their children away from a childhood like yours.
I don't for a second blame you for questioning her, with all her means, didn't at least try to save you from the hell of your childhood.
I wonder that you don't have PTSD seeing them together after what you saw and endured for so many years.
I feel desperately sorry for you and would really urge you to get some support for all the horror you have gone through.
Thank God you married a good man.