I embarked on a site with both shallow and deep metals, unfortunately, the only metal to be found is zinc. I bought up everything I could from merchants, and had managed to equip all my military with steel weapons but couldn't get enough for much armour for them so they are all in leather. (Is this the best strategy, or is it best to have only two or three fully equipped dwarfs?)
Anyway, I decided to dig down and through the caverns to try and find any better metal, and managed to find an adamantine vein. I made the decision to risk it, but to leave a few layers above the cavern floor so I wouldn't breach into hell to soon. Unfortunately this plan didn't work. I managed to stockpile 80 odd units of raw adamantine before it happened. My two miners were killed straight away, and I immediately set dwarfs to masons to block the route into my fortress. I managed to stop them getting to me just, one poor fella built the wall from the wrong side, sadly, but he did finish it just in time to force them to divert through the caverns, buying valuable time for the rest of my dwarfs to finish their work.
As it stands now...
I have ~55 dwarfs total. (thankfully only three were lost)
I'm in a cold biome with liquid water on the surface for a small part of the year, in small quantities. I've had to block access to my only permanent water source in the caverns.
I have ~80 units of adamantine, ~10 steel weapons and ~units of iron and bronze. Military is currently equipped with leather/no armour.
I can't access the caverns or my dwarves will be slaughtered.
I have plenty of food and access to lots of wood and flux stones.
What should I do? I intend to try and take on the demons, but how should I go about it. What traps are effective against them? (I can't access water or magma) How should I equipped my dwarves, and how should I take them on?