To illustrate the author’s calm, contemplative mood
This is the best description for the excerpt. The author illustrates his mood with words that identify his mood at the moment when he wrote it. He has written about his thoughts as well and his view of nature.
Yes.
Think of a thesis statement as something that you know or believe is true. For instance: "The dog is brown." After you have told this to someone who is blind, you would go on to explain how and why the dog is brown. The thesis is the main topic in a story. After the thesis is stated, you would go on to explain how and why the dog is brown.
Run-on sentences make text more difficult to read.
Run-on sentences can change the intended meaning of a text.
Run-on sentences can make a sentence confusing.
Overall, run-on sentences are just a bad idea.