You asked two questions in your original question, and enotes specifies that you are only able to ask one, so I have edited it to focus on the humour in the text. Clearly, if you read this story, hopefully you cannot fail to identify the humour in this story - from its very start, the character of Granny Weatherall dominates the pages and is funny and sad in turn. This of course occurs as Granny Weatherall is trying to make sense of the world around her even as her awareness of what is going on is fading as death approaches. Even the start of the story presents us with a funny moment as Granny Weatherall shows her defiant spirit by her comment about the doctor:
She flicked her wrist neatly out of Doctor Harry's pudgy careful fingers and pulled the sheet up to her chin. The brat ought to be in knee breeches. Doctoring around the country with spectacles on his nose! "Get along now, take your schoolbooks and go. There's nothing wrong with me!"
Of course, what is funny about this is that we think of doctors as being respectful figures in society - certainly figures we do not address and think of like this. The juxtaposition with the term of contempt "brat" and doctor shocks us and makes us laugh by revealing the kind of character that Granny Weatherall is. This does not stop after the first paragraph, but continues throughout the story as we see the irreverent attitude revealed towards other characters such as Father Connolly.