Well, I've left Metalsnakes alone for a while now to start playing Masterwork mod forts. The forgotten beast Kor had the last laugh, I'm afraid. A minor flooding incident left some deposits of forgotten beast extract on the floor of my main hallways. Everyone trekked through it, and everyone began passing out. Most of my population falls unconscious every so often, spending valuable hauling time on the floor. All work has ground to a halt, but we're a duchy now!
Meanwhile, after a few trial and error losses, I've got a Masterwork fort running fairly smoothly. Stizashzon, Kindlehelms sits juuust on the edge of a nasty little biome that's constantly raining this acrid filth that makes everyone covered in pus. Also, clouds of blinding sand roll in from time to time. Despite these challenges (as well as a shortage of trees) the population has risen to about 115. I've got some bedrooms set up, workshops dug, and an arena to train my military.
I've been cheating a bit, but it doesn't always help. What has helped is an enormous granite wall that surrounds everything the fort might need. It's nearly all the "usable" land on the map not getting filth rained on it. I've redirected the river to become a moat around us, but it freezes in the winter. Our water reservoirs are safely refillable from inside the fort and large enough to last years. The soldiers should be up to par soon, once I find all the good ones and sic them on our various prisoners.
We've fended off half a dozen ambushes and one very small orc siege so far. All with the help of whatever caravan was around at the time, but I don't think we'll need them with our defenses set now. Trading, hunting, and fishing are the only reasons to keep the walls open, so I might just turn off these labors and make a guarded passageway out to the depot. I've never survived this long in most forts, much less bumping territory with a Terrifying biome.
I need booze and wood, though, so the caverns need to be dug into. I made an above ground passage directly into the first cavern layer, and am in the process of lining it with traps. Whatever comes up will be more easily dealt with if it's outside my and through a gauntlet of traps.
As of playing now, I set up a danger room and got my militia commander up to legendary in shield user, armor user, and fighter. He's master in axes, too. I'll have a competent military yet, as soon as I can get some marksdwarves to do something useful.