Well I just created this account but never mind...(please excuse my bad english,I am not a native speaker)
I myself have yet to get the 100% but I noticed that there is a tall tower in the Fort which seems to have ladders.I tried to get there but was shot before reaching it( I parked a car next to the base of the tower to climb on it and reach the ladders,since it is too high to jump on it from the ground) But anyways I also noticed that around the fort there are two (that's how many I counted) small tunnels(like sewers) with grids in front of them,while I don't think they are important I though I better mention them instead of ignoring them since everything could mean something.Also there are several containers with the writing "JetSam" I don't know what to make of it but hey it has "Jet" in it's name so maybe they have to do something with the Jetpack Part of the riddle.
I also noticed that the guys in the hillbilly camp(the one with the glyphs) always respawn if you just kill them(has that been mentioned before)
What I also did was looking at the fort from a distance and trying to notice a pattern in the actions the people in it make but nothing special caught my eye besides the three soldiers always walking the same route.I also noticed that there is a baseball bat ON the stone in the cannibal camp. Maybe you have to "sacrifice" someone on it by beating him to death with it?Also has anyone used the internet(the ingame one) by "googeling" key words such as Mount Chiliad,Jetpack or Alien?I for one googled Mount Chiliad,but didn't find anything and when I searched for Jetpack I found a side called "Children of the Mountain"
Can somebody tell me how I add pictures? then I can post some of the stuff I mentioned above,I didn't take a picture of the one with the baseball bat,because I took pictures with my smartphone while I investigated