Thanks so much aeh!
Regarding his reading vocabulary/comprehension...
His teacher (who is nothing short of phenomenal), saw early this year that his reading level was well beyond their second grade class. She created a reading group for him with DD8 and the two highest readers in fourth grade. She assigns them books and meets with them once a week to discuss.
At first, she tried middle school level nonfiction books about space, etc. Then they moved up to Tales of King Arthur (I think their version had a Lexile of 900), which was also deemed "way too easy." Currently, they are reading the original 20,000 Leagues under the Sea. He's able to read and understand it as well as any of the three girls in the group.
When I showed the teacher his test scores, she was amazed that his reading vocabulary score wasn't higher. But I think that much of what you're saying is correct. He relies a lot on the context to get the general idea of what the sentence is saying.
