Whether it is correct to use a comma before a coordinating conjunction ("and", "but", "or", "nor", "for", "yet", "so") depends on the situation. There are three primary uses of conjunctions:
When a coordinating conjunction is used to connect two independent clauses, a comma is always used. Examples:
- I hit my brother with a stick, and he cried.
- The rain stopped, and the sun came out again.
- Should I eat dinner, or should I play a game?
When a coordinating conjunction is used to connect a dependent clause, a comma is never used. This includes both of your given examples. Other examples:
- The boy ran to his room and cried.
- Frank is a healthy and active child.
- Should I eat dinner or play a game?
When a coordinating conjunction is used to connect three or more items or clauses, a comma is optional (though I personally prefer to use one). Examples:
- I bought cheese, crackers, and drinks at the store.
- Should I eat dinner, play a game, or go to the store?
This is a compound (and complex) sentence with two main, independent clauses
Furious, John strove to catch Jim by the shirt
Jim was too quick.
Two main, independent clauses need to be separated by a comma, a semicolon or a period. Effectively, these could be separate sentences, and the punctuation reflects that.
but once more is a dependent phrase that is set off from the main clause by commas because it is parenthetical in nature. Parenthetical clauses or phrases are those that are incidental to the main idea in the sentence and are of a type that could be set off in parentheses instead of commas.
so that he might throw him against the wall is a dependent clause that modifies catch and does not need to be set off by punctuation.
Similarly, in the second sentence, and for the first time in decades is also a parenthetical phrase. At times, such phrases are not set off by commas, but when they are longer or more complex, they usually are.
Some would even put a comma after the word and, rendering it
When they broke apart, the old warrior bled from many wounds, and, for the first time in decades, there was something close to worry in his eyes.
That approach seems too choppy for me.
Best Answer
Please take a look at the sixth definition of and on OALD. The definition states that and can be used to show the result.
In your examples, the two words - and and so - duplicate the presentation of causuality. Semantically, the use of and so is incorrect.
Note that sometimes and so is used not to join two independent clauses.