ELH:

Your DS sounds rather similar to mine. The WISC GAI and FSIQ are similar, and it sounds like the reasons are similar. Also, DS's memory and speed scores were quite low. I suspect a poor rapport with the tester, but also suspect, like you, some hidden 2E issue, which no one to date has been able to put a finger on. The uncertainty is a big part of what's driving us to the JHU extreme (in terms of $).