Update.
I breached the caverns and walled off a huge section. The resources are plentiful and worldgen did just what I asked: a nice flat cavern that is mostly open. I like being able to see almost everything without changing z-levels. I gave up on making tree farms because there is so much designation cancelling because the soil is damp from the water above.
Next was building a secondary entrance lined with cage traps. It was an enormous undertaking; not only building the traps themselves but planning ahead. I built a mass pitting system nearby. OCD also kicks in: I demand stone block floors or smooth stone under all stockpiles and buildings. Obsidian blocks are used because I can mine it out quite easily right now, and it will be easily infinite later.
But there was carnage. I scummed many times! No matter how I fiddled with things, I always lost a dwarf or two even though almost everything got caged. The main issue was the kobold zombies. They retain trapavoid status and ignored locked doors. One of my two axe dwarves died in the end. I thought I had gotten everything under control but that death caused a mini spiral. As things went along, 6 of the dwarves ended up getting married. The two axe dwarves had been married already, and then the two miners married, and then the woodworker married the stoneworker.
After Athena the axedwarf died, it eventually triggered melancholy in Pinkerton the miner. When he died, his wife Petunia followed. She had a baby at the time and dropped it on the floor when she went insane. I was afraid the baby would die of thirst but she actually turned into a child just in time. Meanwhile the farmer/brewer Budweiser went insane, and so did the woodworker/leader Jane.
In the end I only had 3 dwarves. Ares the axedwarf, Marx the stoneworker, and the child. They managed to carry on. First they threw all the zombies into the pit to recycle the cages, then they atom smashed all the leftover refuse. Then they made slabs for the fallen, learned to farm and brew for themselves, and waited.
Migrants came. And the fortress grew. Industry has expanded for a few years and the fortress is quite nice. At the moment metalworks are being built. I don't really have wood to spare, and bones aren't readily available, so I need to make bolts out of metal. There is tetrahedrite to be smelt!
I need marksdwarves. By raising the drawbridge and opening the secondary entrance I can get rid of most zombies on the surface as they wander into the cage traps. However the goal isn't just zombie capture (though they are nice for training). I need to control the surface. I have lost most migrant waves and EVERY caravan to the zombies. I've been able to clear the surface once or twice but it's fairly labor intensive and takes a whole season each time. Also, kobolds and goblins have sent ambushed and they tend to just join the swarm. I need permanent marksdwarves perched on top, and I need to wall almost everything, build a paved road to the border, and generally defend better. Mostly I need to block line of site so the masons can build my huge land bridge in peace. I've imposed a challenge on myself in that I'm not allowed to use any magma until I breach the volcano's crater, so I need to build north.
The fort is 24 strong, with 2 axedwarves and 3 marksdwarves.