Very good, PA, except you got south and west mixed up.
Mongo Valley is in the West (it's a Western setting, after all), and Clakkerz come from the South of Mudos.
It's obvious Stranger comes from the Mongo Valley - that's where all Steef come from. What is more of a quandary is what sort of a life he led before the start of the game. He doesn't like guns, so it follows he knows his fellow Steef were hunted and shot, and that he possibly knew them and was part of their society: but maybe he was rejected from their society because he's too scrawny, and no use as a guardian of the Grubbs. So he built his own crossbow to protect him against Outlaws, then someone suggested he accepts bounties from Clakker Bounty Stores. Whatever happened, it just seems like there's quite a backstory missing.