So, let me make sure I understand - a 7th grader with dyslexia is scoring high enough to exempt English in college? What challenges does his dyslexia present at this point?
Our child too had a very high ACT scores prior to starting high school, but I really didn't consider that particularly relevant for planning high school. It suggested to me that he'd mastered grammar basics, but I already knew that. I considered it more important that we focus on writing including essays, exams, and research papers. And, that we focus on critical reading skills in areas including novels, poetry, and nonfiction. We did not use a formal curriculum in high school (or before that for that matter). The fact that you can customize the education is the best part of homeschooling.
Especially if your child is looking at selective colleges I would suggest you carefully document that he's had strong study in literature from different time periods and regions. As much experience with writing, first drafts, revisions, research, etc. are all really important.
