Do you think it would help if...
They take polaroid photos (or just photos in general) of people whom he met, or are in his life, such as the caretaker, the husband of the daughter. And maybe with him included in the photos maybe sitting next to them as well, and showcasing the flat/apartment interiors as background! And whenever he gets confused, just pull up those pictures and show them to him.
It would kind of derail the movie, I guess..