It's not Richard's job to explain who wrote the Book of Mormon. Even if we don't know who did it, that doesn't mean that "God did it" is the logically compelling argument. It simply means that we don't know who did it, or how Joseph did it. It is enough for Richard to simply say that the evidence doesn't support your theory about the origin of the book.
Sure, his "Joseph did it" theory may not satisfactorily explain what you present as evidence that there is "Early Modern English" in the book, but I'm pretty sure your "God did it" theory also doesn't satisfactorily explain it either.