Mulling over this...I think I'd consider speech and language testing, too, as there is some suggestion of a difference between expressive and receptive language, with a possible relative weakness in expressive language (naming vocabulary, comprehension, writing vs vocabulary, verbal comprehension, and reading comprehension). How'd he do on the the oral language subtests of the WIAT? Your description does suggest a lower probability of dyslexia. The overlap of dyslexia with visual processing disorders is mainly in presentation, not in underlying deficits.
