Subject predicate and order.

A sentence can have a grammatical subject, a logical subject, both as separate entities, or both together.

I have a dog.

In the above sentence the grammatical subject is I, but the logical subject will depend on context. If the phrase answers the question Who here has a dog? then I is also the logical subject, but if the phrase answers the question What kind of pet do you have? then dog is the logical subject.

To scale this up to the level of a story - as you have intimated in your post - a story can have a "grammatical subject" and a "logical subject" as well. If we take the recent Science Fiction film Her as an example, the "grammatical subject" is an artificial intelligence named Samantha, but the "logical subject" of the story is human emotional interaction and connection, or lack thereof.

As regards sentence structure, the sentence should serve the needs of the paragraph and scene in which it is found. Those are the masters it should serve. Reading your above post, it's clear to me that you have an understanding of the S-V-O of a sentence given that your sentences are well-structured. The order and complexity of those sentences serve the questions you are trying to ask, which is as it should be.

S-V-O is just another way of describing the concept of subject and predicate. The three letters stand for Subject, Verb, and Object. In linguistics, this is the more common way to talk about the concept since different languages have different tendencies for word order and most languages (to include English) allow for several variations depending on style and other factors.