Thanks for the chapter.
Uncle enabling Mable to stay as a shut-in is expected. He's at the stage where everyone is rejecting him. He doesn't want Mable to experience the same thing.
Feels like the nephew is the true happy ending for the Uncle. The higher power in the isekai probably realize that he's still miserable no matter how many companions he has, so they send him home to get closure.
Suspect that he wants to meet his family one more time. Then the story will end with the Uncle dead and the nephew hoping that the Uncle returned to the isekai.