Can anybody give me a clue wot to do at the fort?

You don't need the spare furs or anything like that. If you are still in the locker room you can get the suit too disguise yourself as a grunt or bandit or whatever you call them(lol if you go into the cave when your wearing it sky runs into the wall). You can also go back to the locker room again you can get the fuel and I heard there is also a flare gun there too but I don't know where. After that you should be able to figure the rest out. Hope I helped. O also by the way if you constantly go on the rafters and check on the foreman constantly you can get access to a map and his radio thing, but the transmiision is really hard to figure out.

For the flare gun you need to go inspect Skye's lifeboat first; you get the cutscene where Keith says the waves are low and you can leave, but don't. Go tell Skye, then go back to the bandit's locker room and the flare gun will be on one of the shelves to the left.

After eavesdropping on the guards and people from the rafters, in order to get any other items you need to go tell Skye what's going on. There should be a cut scene where Keith tells her about the bandits. Then go back, there should be a uniform in the locker room on the shelf. If there isn't you just need to snoop around some more and learn more to tell Skye. Once you have the uniform and equip it you can walk around in disguise and they can't tell the difference.

For escaping on the boat you need to go to the area in front of the buildings, with the two pacing guards you had to get past first, and go right until you see the ocean. There should be a little wooden ramp. Go down it and see the boat docked there, then get on it and climb around until you get the cut scene and then go tell Skye and then the fuel should be in the locker room. Find out which color mushroom makes you sleep, then talk to the Squad leader (I found him in the potato patch, talk to the other guards to figure out how to get people to eat something, but have extra food on you) and give him the sleep mushroom and he'll drop the key. You also need the sea chart, which is in the Boss's office. He wakes up at 7AM sharp, so sneak into the building before then in your uniform, then take it off and as he's waking up run into his office and take the chart from the alcove behind his desk.

I don't know about the rest of the items, I've only played it through twice and escaped those ways. I hope I was helpful.