jdtm, interesting you say that, because I believe that SID IS high-functioning autism.
I think in some children diagnosed with SID, it is indistinguishable from Asperger's syndrome, which is high-functioning autism.
Actually, your post remind me of our nephew when he was a child. Is he able to carry on a conversation in sentences? As an adult, he was diagnosed with PDD-NOS which is a high-functioning form of autism. But, the big query - is he able to carry on a conversation? Our nephew began speaking at three years of age but echo-talked for two years before he "understood" the art of conversation. Hope this helps ...
Sounds like sensory defensiveness to me, and Sensory Integration Disorder.
We also have anxiety issues in our family and I know that sensory issues are co-morbid with anxiety (although I believe that the anxiety is the "primary" disorder). My sister suffers from mild-to-moderate GAD (generalized anxiety disorder as did my mother) and I believe that my father has very,very minor "traits" of autism. Both my parents have sensory issues. I guess I was lucky - didn't inherit either. To make matters more confusing, there are anxiety and personality disorders on my husband's side. He did not inherit any of these of these disorders either. Luckily, our sons inherited only a "touch" of shyness; not the sensory, anxiety or personality issues. The funny/ironic part of all this learning/information is that I was not aware of any of these issues until my fifth decade in life. We're always learning ....