My father and step-mom have 2 different residences, about 1200 miles apart. My step-mom has Alzheimer's and after a recent visit it seems very apparent to me that her care is too much for my father to handle. She has 4 children that also live about 1200 miles away in a different direction! In the past they would return to our hometown for the summer months. As her dementia increases, we all realize that moving her adds to her confusion tremendously. I have expressed my concerns to my father that he needs to find a place for her to live where she will be safe and he will have to visit her. He continues to think she can stay with him with a little extra supervision. I'm worried about both of them.
Since your father and step-mom have 2 different residences, maybe they could sell both and move into a community that has independent living for Dad, and continuing care living for his wife. That way Dad can develop new friendships with the guys that live there, go golfing, playing cards, etc. but still be able to have some or all his meals with his wife.
The hard part would be to convince your Dad that maybe now would be the best time to find such a dual complex, and for him to do it now while his wife can still bond with people, such as the staff and new residents. One question would be where.... I would go with whatever area has the best complex for both.