by S Richardson
Your suggestions about Japheth seem to be slightly tainted! Pawthaw, or Pahtah, means to open(roomy) in the figurative sense(in mental or moral sense), to be simple or in a sinister way, it could mean delude: allure, deceive, enlarge, entice,flatter persuade or silly(one)!
Now, since the word territory follows, there is no way that it could be talking about the MIND! Put everything in context, honestly, how in the world did you come up with that? Even afterwards it speaks of him "dwelling or living".
This is indeed referring to geography, not the mental superiority that you are hinting at! Let scripture interpret scripture.