MrsMandy,
I'm sorry it's taken a bit for me to get back to this thread. As you're pondering ideas, you had asked about DITHR for a 9th grader, for the literature portion. So, here is a link that will help you see how you could easily use that for a 9th grader for literature study if desired. Link:
viewtopic.php?f=6&t=7765
The writing that will be within each of the guides actually would be good for your high school student. For example, within CTC
Write with the Best does extend up through grade 12 (supposedly, which I think is a stretch), but it would be good for a 9th student who is not strong in writing. It does a good job of strengthening descriptive writing skills. Then, in RTR, you could easily use
Medieval History-Based Writing Lessons for your then sophomore student, just following the extensions in our plans.

This writing course strengthens the forms of informative, persuasive, and expository writing. When paired with the writing in CTC, you'd have coverage of the various forms of writing.
In Rev. to Rev., you could weigh whether you needed to add something writing-wise to the
Exciting World of Creative Writing. Cathy Duffy does say in her review of it that she believes it to be worthwhile for use by high schoolers as well. At that juncture, you may desire a bit more focus on essay writing, using something like
The Elegant Essay for a year instead of, or in addition to, the writing portion within Rev. to Rev. Along with DITHR, dictation, the assigned written narrations and other written work in our guides, the writing courses in our guides, vocabulary in DITHR and in other portions of our guide, and Rod and Staff English, you would have a solid English credit for your son's 9th grade year (not to mention a very solid founding in literature/comp./and grammar).
As your son moves into the 10th - 12th grade years, you would want to look at other literature options for deeper study beyond DITHR. Honestly, many of the courses we looked at for high school level literature study were less rigorous in many ways than DITHR, or else spent so long drawing out the study of a novel (albeit with good questions) that the love of reading the work would be lost and the book would be dissected too far! This was my own experience with literature in high school, which did not develop a love for the classics in me! Spending 9 weeks on one work of literature is too long!

The other thing that we found is that some literature programs gave almost no guidance in reading a book, leaving much of the interpretation up to the student. For those who haven't had much formal literature study prior to this that doesn't help much either. The last options we looked at had so much composition tied to the readings that the composition aspect took over the program. So, we're still seeking a balance in these areas as we look at high school level literature options for our own son. SMARR and LLATL Gold are choices that we are leaning toward with our own oldest son, definitely with some additions and subtractions to the novels listed in those guides, and with some possible additions or substitutions to the writing portions.

Of course, we won't know until we try, so these are just our thoughts at this juncture in the journey.
I do think you could plan to do some beefing up to get .5 up to a full credit of the fine arts for art appreciation in RTR, and .5 up to a full credit of a fine arts for music appreciation along with Rev. to Rev. It would depend on how much you add. So that would help there.
You could use whatever science you felt met your child's needs best. I will mention that we are using
Integrated Physics and Chemistry from pacworks this year and really liking it with our 9th grader. For the lab portion he is doing the labs from Exploration Education (just Days 4 and 5 each week), as he had already done the other portions of Exploration Education when he was younger. We do plan to use the
Biology and Anatomy and Physiology from pacworks next year for my son in 10th grade, along with some Castle Heights labwork for Biology. I just share this as it may be an option to ponder as well.

If you plan to use Apologia, then that would work fine.
Another thought we had as far as Personal Finance credit goes, would be to do the Financial Peace University course, if it is ever offered at your church or one near you. You could add some other material to round it out if needed, but doing Financial Peace is one thing we had considered. We have not gone through the course ourselves yet to fully know whether this is a good option, but we have heard good things about it. So, I share it as something worth pondering too.
Anyway, I'm not sure if I have answered your questions. Hopefully, this will help as you ponder.
Blessings,
Carrie