Language delay or something more?

I have a 33 month old son and my biggest concern is his speech.  He has about 100 single words and has used a couple of two and three word sentences.  His understanding  is excellent and he can follow detailed commands such as "go to your room get yellow car and give to daddy."  He can point to items and knows his shapes, alphabet, colours, numbers and body parts.  He waves bye-bye, is extremely happy, cuddly and lights up when he sees me or his father.  He points to bring things to our attention.  He plays well with his sister.  He laughs appropriately and has no issues with new environments.  He is curious, energetic, gentle and rarely throws tantrums.

I have him in a weekly Early Intervention playgroup.  He attends a music class for NT children and participates well. He attends swimming class weekly and enjoys it.  He attends speech therapy fortnightly.  He has been assessed by a child psychologist who said he had a language delay.  His pediatrician agreed with the psychologist, however his speech therapist hinted at autism as did one of the therapists at Early Intervention.  In terms of his gross motor skills there is no issue and he is a great eater and sleeper.    


The things that concern me are:

Delayed language for his age
At times holds his hands to his ears when he anticipates a lound noise
Plays with toys such as blocks, puzzles, cars but does not role play with them
Sometimes throws his toys and thinks it's funny
Will not always turn when called especially if he is focused on a task
Can get stuck on a particular toy/task
Does not line things up or spin wheels
Makes eye contact with immediate family but ignores other people
Plays side by side rather than with other kids.
He can not answer yes or no questions
Occassionally walks on tiptoes.  
Has a habit of throwing tan bark when at the park
Does not like to be held by people other than immdediate family (will scream and pull away, if attempt is made).

Is he autistic?