You received great information above. I'll just add a few quick thoughts -

Is your child a Davidson Young Scholar? With WISC-V scores of VSI 151 and FRI 155 I believe you could apply to the DYS program; The DYS Qualifications are listed here.

Pearson provides some general background on WISC-V scores here, showing how the various scores relate to each other.

You mentioned "variable" and "inconsistent". Are you familiar with the concept of Asynchronous development of gifted kids?
- Link to NAGC description here.
- Link to book "Asynchrony and the Gifted Child" here.
Beyond the 2e diagnoses, asynchrony may help explain some of the variability/inconsistency that you see.

You might want to delete the score detail from your post(s) to help preserve your child's anonymity (consistent with this post and board rules).