Smb, I am sorry to have gotten side tracked from your most questions, I guess in part because I felt they were clearly dealt with by early responses. He needs to see an appropriate professional urgently.

If you want to pm me about where in Australia you are I may be able to suggest someone. I guess some obvious questions that would weigh on my mind in choosing who to take this to are

was psych #1 a gifted expert?
What made you choose them?
Have they provided any answers you were hoping to get?
Have the answered direct questions helpfully?
Do you trust them? This result?

This would influence whether you go to them for more help, or at the other extreme whether you get a fresh IQ assessment, which would have to be on the SB5 if you want it done soon. You also need to consider whether you need to be seeing someone 2e savvy.

I would probably start with a really good developmental paed, if they suspect something quirky going on they may refer you for assessments that will include some form of iq assessment. Or they might refer you to a psychiatrist.