Hereditary Sensory Autonomic Neuropathy
You all should look into a group of conditions called Hereditary Sensory Autonomic Neuropathy. A lot, or almost all, of the symptoms fit the bill. A lot of the kids I've read about could possibly have one of these HSAN conditions. To be diagnosed they would have to have missing or fewer sensory and/or autonomic nerves. The only way to find that out is a nerve biopsy, but they can do nerve conduction studies and go off the symptoms your child has.
Also conditions such as Cerebral Palsy can cause sensory problems.
I have a form of one of the HSAN conditions. My daughter might also have. They were supposed to be autosomal-recessive, but now with my daughter probably having they may change some of the genetic information. Anyway, I just though I would mention these group of sensory and autonomic conditions because I didn't see them here and they fit the symptoms.