Learn English – What can “little silver jet” mean in this sentence, as something that interested a baby when it “fell to the ground”

Literal language implies a text, in which the words mean exactly what they are supposed to, whilst figurative language contains figures of speech, such as similes, metaphors, hyperbole, personification, alliteration, etc.

Here, in your case, there's no figure. You see, like you've already mentioned yourself, the sentence means that the girl believes that the mother could have died while giving a birth to her son clearly. Therefore, this sentence "Delia's resentment toward Eddie could be traced back to their mother's death." is literal.

Moreover, whether the boy had been the reason to his mother's death, it doesn't matter, but the way the writer describes the story, and their word choice determines if the sentence is literal or figurative.

For example, if the author had written:

Delia resented toward Eddie, since she believes that the death's snake has crawled in Eddie's spirit while coming to the world.

OR

Delia's resentment toward Eddie could be traced back to Eddie's birthday when her mother left the life as Eddie grasped it too firmly.

(First of all, both of my examples are mumbo jumbo, just for instance) Well, the death of the mother would be related to the brother's birth:

1- metaphorically (in the first example)

2- using personification (in the second example)

In this case, the text would be figurative.

As per the excerpt, the text is indeed figurative, since there's at least one simile within the text:

"..it seemed, to another country from where she looked at me with increasing annoyance and contempt."

For a man to "keep" a woman, or for a woman to "keep" a man, means that they are having an illicit romantic relationship and the person doing the "keeping" is paying all the bills. Like if a man has a girlfriend and she lives in his house and she doesn't have a job and so he is paying all the expense, than we say that he is "keeping her" and that she is a "kept woman".

Note that this term is not used for a wife, where traditionally the husband was expected to provide a house and pay the bills. It is sometimes used for a husband if he does not have a job but his wife does. But usually in this case it's used as a simile, that is, we don't say, "He is a kept man" but "He is like a kept man." He's not REALLY "kept" because they're married, but they act like he is.

The Bible quote you give, "the Lord bless you and keep you", is archaic language. No one uses the word "keep" today to mean "protect" except when quoting old text. Someone might say "keep you safe" or "keep you from harm" or some other longer phrase.