I recently learned why I haven't been able to feed Barrett things like meats, apples, carrots and other raw vegetables. I took him to a speech pathologist who specializes in feeding and she said that he chews like a baby who is just learning to eat table foods. He doesn't use his tongue or the rotary motion that allows food to be ground up smaller. So I guess now he gets to have "chewing therapy".
I didn't think too much of his chewing abilities until I noticed that his little sister with no molars could chew up things he couldn't. I hope if we can get this solved we can help him to be better nourished.