How is it going now with your son? Your comment sounded like you were describing my now 5 year old. I'm sick with worry. Any thoughts?
Has any one mentioned Aspergers or High functioning autism. Many of these kids only want to play in specific ways and with certain kids that will play in "their" world. The dysgrapia - fine motor skills, is also another indicator of Aspergers. The fact that he will not respond well in conversation and eye contact is also classic signs of aspergers.
I have been having trouble with my computer so I hope that you read this posting. I suspect strongly your son is suffering from social phobia - selective mutism to be be exact. Please "google" the term "selective mutism" to find information on the internet. Many educators and medical personnel are not aware of this disorder and so, it can be difficult to find a correct diagnosis. With proper treatment, the prognosis for sm (as this disorder is commonly called) is excellent. Please let me know if I can be of more help as I have had a lot of experience with selectively mute children.
It sounds like he might have social anxiety disorder-- which is an extreme form of shyness, bascially. I think you should bring him to a child psychologist or child psychiatrist for an evaluation. If he does have social anxiety disorder, this can be treated. Good luck.