One thing I am figuring out, narration skills (oral or written) cannot be rushed. They come in their own sweet time, and they need to be encouraged along slowly, which is tough for me sometimes, as I am admittedly not the most patient person. I think that you have high expectations for your ds, which is good. I think your expectations may be exceeding those for written narration within the CTC guide. Taking a step back, if you read this below (which is the 1st week of written narration plans in CTC), can your ds do this, especially considering the portions noted in color?
To prepare for writing your narration, think
about the questions below.
If you do not know
the answers, find them on p. 30 or 31 of The
Story of the Ancient World. Ask yourself, Who
entered the ark? How was the door to the ark
shut? From where did the floodwaters come?
How long did the downpour last? What
happened to the living creatures on earth?
How high did the floodwaters rise? What did
the waters carry along with them? How long
did the ark float? Why did Noah send out a
raven? What happened when Noah sent out
the dove? Why was Noah filled with joy when
he saw the olive twig? When did Noah come
out of the ark?
After you have thought about the answers to
the questions, turn to Unit 1 in your Student
Notebook. In Box 4,
write a 5-8 sentence
narration that begins with, Noah entered the
ark... When you have finished writing, read
your sentences out loud to catch any mistakes.
Check for the following things:
Did you
include who the reading was mainly about?
Did you include what important thing(s)
happened? Did you include how it ended? If
not, add those things. Use the Written
Narration Skills in the Appendix for editing.
I think sometimes our expectations for our dc are on a sprint race, while our dc's are on a marathon - but slow and steady wins the race too!

When I am feeling frustrated, I pretend to open my HOD guide and read the goals of the plans and the progression of skill I can expect with fresh eyes. I do the same with things noted in the Appendix. I usually find I somehow expected my dc to be far ahead of the guide's expectations, and find that in fact, they really are doing what the guide is asking them to do.
In regard to Written Narrations, the Appendix says this...
Written narrations allow children to use their writing to share their own version of the passage they have just read or heard with accuracy, individual personality, spirit, and originality.
This is a sentence I personally have reread and reread. It made me realize I was expecting my dc to narrate by giving a summary narration every time, or I was expecting them to narrate what I would have narrated. In fact, I was sort of waiting, waiting to see what they "missed" in my opinion, and pounce upon that as if it was an error. The truth is, if your ds is writing a 5-8 sentence written narration and it fits with the given topic at hand, whatever those sentences are are correct. In fact, even a little leeway is given for "individual personality" and "originality".
Likewise, the editing skills are to be learned one at a time. Again, I've needed to reread this many times, especially this part:
The skills listed below range from beginning writing skills to more difficult writing skills that require knowing higher levels of grammar, usage, and punctuation. Skills are based on a continuum of increasing difficulty, so related skills may be spread out to be placed where they each fall best on the overall continuum. For example, the third skill on the list is beginning and ending sentences correctly, as well as correcting sentence fragments. But, fixing run-on sentences, which is a related skill, is not addressed until the seventh skill. For this reason, it is best to read the list over in its entirety, so you can see the overall flow of the continuum. Focusing on teaching one new numbered skill at time in the order it is listed will help you to avoid overwhelming your child with too many skills at once, and will give your child a manageable plan for successfully learning to do written narrations.
For new or struggling writers, you should start with the skill listed first on the list below. Once that skill is mastered, move on to the next skill. The skills should be cumulative, meaning each time a new skill is added, the old skills are still required. You may either make gentle comments as students are writing each sentence of their narration, or wait until the narration is complete to make your gentle comments then.
This helps me not to become overly aggressive in trying to rush my ds through this lengthy list. It reminds me that one skill is to be learned at a time, and then and only then, does he progress to another one.
So, if your ds is writing 5-8 sentences for his narration that relate to what he has read, keeping in mind some originality is allowed, and if he is even working toward success of 1 of the things on the written narration list, he is in fact doing what he is to do.

I struggle with this sometimes too, but I am finding that by focusing on 1 thing and then truly mastering it, instead of focusing on an entire list of things all at once, truly does move my dc along more quickly than expecting it all can. Maybe I have only managed to describe ME here, in which case, you already have some excellent advice on what can be tried, but in case you may have some of my tendencies, I have posted this. Please just ignore it completely if it does not apply to you!
In Christ,
Julie