I'd suggest looking into the BrainPop app as it has videos on a wide range of subjects with some good depth in science. Each video has a quiz associated which is a nice way for your kid to gauge whether they followed the video or not. After having Amazon prime for shipping savings, we recently realized it also includes access to a wide range of television series, of note are quite a few science themed ones like How Stuff Works.
My DS7 is also a video junkie, and spends much time looking for math and science videos; part of it is he has a corrected vision problem and partly I think because he is more extraverted he enjoys seeing/hearing other peoploe tell him things. So, if you haven't had your son's vision checked, it could be one area of impact on his reading interest level.
As to the WISC results from what I've seen, average PSI and WMI are almost "standard" discrepancies for a large number of gifted kids which is why the GAI index exists.
