What to do for my kid ?

I am father of a three years kid, who is going to be four in this December. He is diagnosed as PDD NOS and still can't form a three word sentence. He has not asked us a single question till now. However, he knows capital and small alphabets, can count upto 150, knows all colours, shapes, all objects around him. He momorises page numbers of books, which are more than 100 pages, means you ask him "which page has xxxxx pic ?" he will tell you the page number accurately. He can also momorise colours of alphabets of his children books. We are doing many things for him, like showing him to specialities, trying multiple diets like gfcf, scd etc. and also he is going to a special school. Does anyone come across with this kind of kids, how can i improve his language ?What to do for my kid ?
He sounds like he is doing well !

At three Thomas pictured left couldn't say anything and now at aged 10 can say two words, all i can say is just keep talking to him but to be honest he sounds fine to meWhat to do for my kid ?
Does he get speech therapy at school? Make sure on his IEP he is mandated for speech and also that HE GETS IT...often speech therapists are overloaded and neglect kids on their list. Make sure your son is getting the therapy he is mandated for.