Yes I think you are right about it lowering his scores, sadly no test is perfect and they don't take into account that he sees things differently.
Dd1 had an IQ test when she was 6, she was not doing well at school and was disruptive and very challenging at home, people told me it was because she was bright so we paid for her to be tested. It turned out that her IQ is in the 99th percentile.
However that knowledge did not really help us, it didn't inprove her behaviour or get her better support at school.
She has difficulties with Theory of mind and empathy amognst other things. We are convinced she has an ASD but now at 22 it is unlikely she will ever get a DX.
I can totally get why you are looking into these things and at the end of the day it doesn't matter what anyone else thinks.
You are doing your best for your Ds and that is all any of us can do.
Good luck with the visual assessment.
I know what you mean about running out of days, I am supposed to be getting Dd3 back to the GP to get a referal to someone about her joints, she is getting pain in her ankles, is hypermobile but has been discharged by OT
.
Am off to bed now will check back here again tomorrow
.