My, that is a big baby! We had a 34-weeker, too, but ours was just about half the size of yours.
Has he ever been evaluated for PANDAS (Pediatric Autoimmune Neuropsychiatric Disorders Associated with Strep infections)? While the most publicized behavioral symptom associated with PANDAS is OCD, ADHD-type symptoms and learning difficulties, especially in handwriting, have also been reported. I'm not an MD, but his early infection history, particularly scarlet fever, in combination with the ADHD, handwriting, visual issues make me wonder if there might be value in having a neurologist evaluate him for PANDAS. With all those food sensitivities in infancy and early childhood, he sounds like he might be predisposed to autoimmune syndromes.
If you do not see anxious/obsessive/compulsive symptoms in him, this is much less likely.
Multiple early ear infections can often have an impact on phonological processing, due to difficulty hearing the sounds, which can then surface as a reading disability later on.
