Skipping all the religious nut accusations, I'm going to focus on the one thing I think should be addressed RIGHT NOW for this child. Reading. You say he doesn't read as well as other children his age, and this concerns me. That is absolutely not typical of well home-schooled children. My niece was reading chapter books at 3, got her black belt at 12, and is enrolling in college courses at 15. She's an incredible artist, and has taken a number of community art courses. Her brother isn't far behind. He was reading chapter books at 6, got his black belt at 10, is very active in local little league baseball, and will be enrolling in college courses himself as soon as he decides what he wants to learn more about that he can't get at Kahn. Smart money says it'll have to do with Engineering.
Before you ask, their mother (my sister) did not go to college, nor did she attend any secondary school. She didn't load up on extracurricular activities in school, and she didn't marry into an intellectual family. Her husband is an MBA, but he directs their learning far less than my sister. It's not impossible for a high school grad to learn how to do it right, but it's not easy to actually *do* it right. You have to be willing to let them go learn. Both children are far more outgoing with people of all ages and flavors than most adults I know. They are well spoken, polite, and fit well into almost any civilized conversation.
Get your grandson to read. That's critical at this point. Throw the chores out the window if you have to, let him skip church to read, let him read all night in bed (for now), but put something in his hand that will engross him. Harry Potter, The Hunger Games, Artemis Fowl, *anything* by Rick Riordon, just get that kid reading something besides the bible. Now is NOT the time to censor his reading, it's time to let it go. All the books mentioned above are great for pre-teens and young adults, though perhaps the Hunger Games could wait a year or so.
And mark my words, if religious censorship is the reason he hasn't read these books already, then I'm guessing chemistry is not going to be a good choice anyway. Too much science, not enough faith.
Home schooled children don't have to be idiot god-botherers, and they don't have to be idiot hippies. They can be very intelligent, creative, and amazing. But only if their parents *LET* them. Don't direct their learning, EMPOWER it. There's a big difference.