Interesting book (Public Board)
I read a couple of pages and he does seem knowledgeable but I doubt he was a high ranking member of anything. I searched on Schnoebelen and couldn't find anything personal about him or his family, but he has a lot of videos and books. That's all I get from a Brave or Google search.
What Schnoebelen has to say seems valid, but you really don't know who he is.