Various questions about basic rules

"Skiddy" Could have stolen the map from a prominent merchant trader in barter town thinking he could make a pretty penny off of it and fled. Only this old west style cattle barron esq merchant boss sent a bounty hunter to kill "skiddy" and recover the map. Problem was there was a group of excavators doing buisness with him at the time that made off with the map into the wastes. It would explain the use of the dune buggy as a drive by vehicle. They are very expensive rides and much saught after in the wastes, bounty hunters are know for using them in my campaign. Once the party gets to barter town and thinks they are safe and can off load their loot in relative peace is when the cattle barrens men will approach the newcomers. At first they may not know who they are, the bounty hunter may not have told his employer of his misfortune, or maybe he did and these men want to question the group based on the description that was given. In any case the barron is going to want his map back, and will stop at nothing to get it back, goonies style! You could even make an "it" like sloth as a body guard to the barron. you could even link the bipedal rats to this barron if you wanted to. They could be working for him trying to uncover some large cache of relics that was stashed by some long forgotten pirates off of lake mary jane. that map could have hidden clues in it that could lead the barron to this treasure trove of relics and make him powerful enough to buy a some army and dominate trade in this region by force.

hope this helps you out maxstone. its just and example of where the story could go and i encourage you to come up with your own unique story. But of course if you want to use this one or aspects of it by all means please do so. Just let us know what happens next. As the story is really good already!