Thank you for your question!
One of the most important accommodations you can give your son, which is possible through homeschooling, is by going at his pace. The beauty about CHC's curriculum is that you can go at the pace of your child, even for your child with special needs. You will probably find that he will work at a slower pace, often needing more reinforcement and practice. Sometimes you might need to divide his assignments into smaller chunks. At this point I would not worry about his being up to grade level, but being at the level of which he is capable. If you feel that he is getting overwhelmed with his learning, slow down. If you feel confident that he seems to be grasping everything, then definitely move on.
Another important aspect is making sure that he has plenty of hands-on and visual aids when he's learning anything, particularly abstract concepts. The more concrete you can make his learning, the easier he can visualize and understand. For instance, with math it is important for him to have manipulatives and do activities that help him use all his senses. When he is learning his spelling words, it's important that he can see the written words, touch the individual letters and make the sounds out loud. The more you practice and enrich his education both inside and outside the classroom, the easier it will be for him to remember what he is learning. Reinforcement is very important for him.
In terms of addressing his dysgraphia, it is apparent that he probably struggles with putting his ideas down into writing. Focusing on one thing in a group of jumbled thoughts, is probably difficult for him, particularly with the ADHD as well. At this point, I would not worry too much about his handwriting. That will come with practice. I know some students, who never improved with their handwriting, found it easier to type on the computer. This might be a useful idea sometime down the road.
When you are teaching him writing, it is important to first help him find what he wants to say. If he is telling you about something, help him summarize what he is thinking. You can do this verbally with him at first. For instance, you can ask him what the learned at the field trip. Encouraging him to talk about it, and gently guiding him into thinking about what he as learned overall is important.
For practice, I would first begin by having him copy a sentence that you write for him. Slowly increase the numbers of sentences he has to copy. Gradually you can have him start writing down his own ideas or thoughts in 1 or 2 sentences. As he writes down his ideas, tell him to say the words aloud as he writes. Maybe he would like to draw a picture, along with the sentence, to help him express what he is thinking. You could invest in a tape recorder, have him dictate what he learned or read, and then listen to it, maybe writing a sentence or two down. As he becomes more comfortable doing this, you can gradually have him practice more writing. Sometimes it will be easier for you, if he verbally tells you the answers, instead of writing them down.
Visual graphic organizers can be very helpful as well, such as the Venn Diagram and the mind map. This can be helpful in his reading. Draw a circle in the middle of the paper as the main idea, and then from the main idea he will provide supporting facts, so that it will look a little like a spider. You will definitely need to help him organize his thoughts, and help him focus, through practice, much warm encouragement and praise.
God bless you and your family!