Dad stage 4 kidney disease, dialysis soon. He cares for wife who is incontinent, non mobile, dementia. When should he go to a facility?

My dad thinks he can do it all. His kidneys are functioning at 19%, port is going into arm for future dialysis. Mom uses walker, incontinent, and has dementia issues altho she refuses to be tested. Dad is exhausted shopping, cooking, cleaning, laundry, and just about everything for the both of them and will not leave to get much needed rest. Mom keeps waking him up when he sleeps. I want them to move to assisted living, but he doesn't want to. He has been asking for help but now he is afraid to move. What can be done? Any advice?