He's fine with pretty much anything, including long division, as long as it doesn't involve him writing anything down. He can sound out nonsense words and long words in science texts given time. He doesn't always get them right, but generally close enough following phonics rules.

I've heard that dyslexia and dysgraphia tend to go hand in hand and that you generally don't have JUST dysgraphia. I don't know much about either subject though since I haven't hit this 2(or 3 or 4)e issue previously.