In order to figure out what his full-scale score would have been given average performance on coding and symbol search, you would take the sum of scaled scores on the first six subtests and add 20. That would give you 123. Then you would look that up in a table to find the correspoding FSIQ.
You can't add scaled scores to the composite scores.
GAI=154 is quite high. He is certainly HG+. Average performance on the two missing subtests would probably yield a somewhat lower FSIQ. Maybe Dottie could look it up for you.
