Will promises his dad when he lay dying that he would take care of his mother and sisters—he says, “even if I died of working.” Why did the author choose “died” in this phrase?

"died" is hyperbole

Explanation:

Here, it is trying to say that it does not matter how hard he has to work, that he will, in order to take care of his mother and sisters

what is a theme?

ans: the implicit idea of a written work of literature is called a theme.

so, the only theme of "birdfoot's grampa" by joseph bruchuc is that as a human being one should always remember the value of every life on earth.

the grampa is stopping the car again and again to save those little toads from washing away in the heavy rain is an act of kindness and humanity.