A lot of dog breeds do well with autistic kids. Dogs do not require verbal communication and often can establish a bond when the rest of us cannot.
To determine what breed would be best, I think you need to look at other factors. Are they in an apartment or a house? Is barking a big issue?
I would not recommend anything small like a Maltese or Chihuahua because of your comment about throwing his iPad. A medium sized dog would be best, preferably something affectionate that will want to lie around with him.
A Brittany would be great if there is enough space. The Cavalier and the Bichon are also good choices.
Just look into other requirements. Many dogs will be happy to be his companion.