Hi Mk,
I wouldn't rely on a screening alone to make a diagnosis, or to rule one out. I would want a full evaluation (and that will include IQ and achievement testing as a matter of course). Is there a children's hospital in your area that has an autism center? That's where I would go, and I'd make the appointment for an evaluation ASAP (they often have a 6-month wait). You want someone who's seen the full gamut of how autism presents to make some important distinctions about your DS.
I would also not go to an OT for ABA therapy. You want a board-certified behavior analyst (BCBA) or a Ph.D. psychologist directing an ABA program. It is very possible for a therapist to screw this up if they don't know what they are doing. An OT typically has a bachelor's degree, and no training specific to this task.
It is very hard to distinguish the unusual behaviors and interests of a highly gifted kid from those of a gifted autistic kid. My DS's interests were not age-appropriate, either; this was both because he was gifted AND because he didn't have a sense of play or an understanding of how to engage with peers. Professorial behavior is not a social plus in kindergarten; a non-autistic kid may adapt much better to what peers want to play than an autistic kid. Again, I wouldn't expect EI to have a handle on this; I'd want someone who really understands autism and has seen some gifted kids with autism to help you figure this out.
HTH,
DeeDee
