I know this is an old post but I couldn't read and not reply.
It sounds like you have a very bright lovely boy on your hands there.
I have a child who is almost exactly as you describe He's 3 - very advanced with language, self taught reader, super engaged and interested in adults and older children, savant type skills since 12 months old.
My little guy doesn't have temper tantrums or issues with change at all BUT
He does have aspergers!
I hate to say that my alarm bells are ringing loudly when reading your posts.
With holding your concerns to your doctor is not a wise thing to do. If he does happen to have ASD it won't go away by not dealing it with it or saying anything about it. It will just be lost time that you'll be kicking yourself for later down the track.
When my son had his IQ test (much after his ASD diagnosis) there were not dips in his IQ profile. He hit ceilings on all but 1 subtest and was confirmed to be EG evenly across the board.
It would have never identified his ASD.
If I were you I'd ditch the IQ testing (because in the scheme of things it doesn't really matter at 2 to have this) and get him tested for ASD.
There is a chance that his IQ test won't show anything and you might find yourself walking around with a big happy 'my child is a genius!' when really you may have something far more important going on.
