He could make his father regain memory, ask him about everything then reconfirm it with the living. Why chose to trust strangers and overcomplicate things???
They made this show difficult to be likeable because they mixed heartwarming-life genre and thriller. Audience who were up for the first may find it's difficult to enjoy the latter and vice versa.
https://www.hbomax.com/id/en/shows/fifties-professionals/3e0aeabf-c450-4577-b4c7-5517dda72f7a