@JodiWilson -
Thanks for the great write up. I think you explained the issue and your attempts at the solution. I believe that you have everything figured out (not to your liking) about the way Canvas operates. I use classic quizzes, but always with one attempt. so, I have never tried to do what you want. If I get some time I may try out some ideas, but I think you are correct and what you want is not possible.
Edit: your first question is you may have missed the setup forwhen the students can see the correct answer. below is the setup I used to get the results discussed below

I went and tried out some ideas. I can get you 90% of the way there. The only thing that is not possible is the viewing of the correct answer comments on questions that are missed (note this was all done with a multiple choice question).
For the overall comments for the question. The general comments show up regardless of which answer is selected. The wrong answer comments show up if the question is answered wrong and the correct answer comments show up if the question is correct.
For each individual answer, the comment correct or wrong show up depending on the answer.
However, if a question is answered incorrectly after all attempts, the correct answer is shown, but the comments for it are not shown (over site on Canvas's part, but it won't be fixed now). Your only hope is someone knows how to do this with New quizzes.