i would have thought you'd have encountered this so far in your other Settlements, Splint... There isnt much armor available and those that are available you get from trading, as it is in the tabletop game of Necromunda. Since I believe that there has been 3 years of this settlement played before you (correct me if im wrong), the Guilders should already be arriving.
Not being able to play with your regular playstyle should be a NUMBER ONE expectation from playing in a succession game. You should at least play one year, attempt not to die and hand the fort on to someone else, hoping that by the time you get to your next turn you will be able to try some more armored combat. I would guess you will still be dissapointed when you use the armor we have added as is works differently to regular DF armor (stronger but with less coverage %), and again we feel it is quite true to the tabletop game.
You can make leather and chitin armor which should protect you somewhat from wild animal attacks, and bone helms to go with them. Ranged combat is of course favoured against scavvies and outlaws. Sounds like tahujdt has done a good job of training the ranged guys. Set up some fortifications instead of armor and you wont be disappointed.
as humans would logically figure out a way to make ok armor
Try the junk armor, its about as good as Copper Breastplate. Underhive Settlement is supposed to be about survival. Setting up the foundaries in the 40k universe to product combat armor would certainly not be a easy task. I was personally for firearms being only available through trade as well with your only manufacture being ammunition.