Why was she sawing the wood?

Perhaps he knows that Ellie wont live too long in the current situation since his smile dropped when he looked at the photo and then back at Ellie? Or maybe the author added this scene because it represents the author wanting to go back to when the author was younger and change things the author can't fix now or spend more time with people the author adore?

In Section 3, we saw her going from a gloomy mood to a brightened expression after receiving the book.

This happens in real life as well. Many older people know they do not have much time left, and the things that once brought them joy no longer satisfy them. Is it like this in Up too?

They know their time is up, ( NO JOKE INTENDED...) So they will never finish their dreams. This is turning into an inference but it's too good to stop... As these two grow old, we see that they never went on an adventure. Maybe the book reminded them of what could have been. The director of this movie.. Was this specific part perhaps based on one of his relatives? In real life too, old people are unable to do things that they know they cannot. Was that the backstory of rejecting the book?

DO YOU SEE WHERE I'M GOING???

The wife was the only person who could have been with the husband, they're p e r f e c t.

The husband later on becomes a grouchy person, after the passing of the wife. Why? Because the only thing that he loved was gone. This is about their personalities, their design reflects them. After the wife passes, he becomes a block of iron. He comes off as rude because he lost the only one he truly CARED for. AAAAAAH!!

Why didn't their parents visit them when they were young?