I think "using his passion" to teach him doesn't mean taking his interest and applying it to plain regular lessons (like super-hero math).  It means to look for the things he's getting excited about.  For example, if you can get a kid excited they start talking more, which leads to better vocabulary, which leads in turn to better reading and writing.  

I don't fully subscribe to that method, but I read a lot and I think that's a misconception.  

Youth lives by personality, age lives by calculation. -- Aristotle on a calendar