Hi Julie!! Welcome!!
I don't know if you have been to your state's web site or not, but you can look up your state's academic content standards for a specific grade. <at least I know that you can for Ohio, where I am!>
Just type "academic content standards" and your state's name into the google search engine. If you want specific information, you can add "7th grade science" to the search. It might help when you are trying to plan curriculum for home-schooling.
I know that several people here have hired tutors for their kids, usually in math. I wonder if you could find an undergraduate or graduate student who would be interested in tutoring your DS? Or maybe a retired middle school or high school teacher? Just a few suggestions from someone who has not had to face these particular challenges yet.
We are not quite there on the whole home-schooling issue. We are still trying to work within our local school system. However, we may face in the future many of the problems that you mentioned. So I am interested in any responses as well. We have many home-schoolers here, so I'm sure that someone will chime in soon...