I don't really believe that intelligence can be quantified. IQ measures a few specific skills - it doesn't measure anything as broad as "intelligence."

Anyway, Elon Musk strikes me as, honestly, really similar to most of the college dropouts I know. They've picked up some knowledge in school, some from the school of hard knocks, and they know some stuff. But since they don't have a fancy degree to say it for them, they work really really hard to show you they can see through the bullshit and behind the curtain. And because of that attitude, they make clever insights and stupid mistakes in about equal measure.