Why would you put effort in P3-5 for a query with on average less than 15 daily searches, if you already rank for it in those positions? Consolidate that ranking, try expanding your reach.

Don't do futile long tail sweatshop work. If the "opportunity isn't measured against search trends, the opportunity maybe just is not as big an opportunity as it has been made out so far (without anyone checking the search trends).

But maybe there's more in it than just that exact term. Go after it. What is he most known for? His YouTube.