Quarantine and mark off the miner and antisoot until further notice, block off smelting operations in the forge. Assign 5 healhcare specialists and 1 magician keep the miner healthy and study the antisoot. Write and send a letter describing these events to the mountainhomes, as well as requesting raw cotton, along with cotton seeds. Send 5 of our miners to dig out a dry, cool, and dark chamber for explosives. Get our engineering+crafter+hauler+metalsmith team back to work on the rifling and die drawing machines. Assign 5 new Metalsmiths to produce blank brass circular dies for the machines. Assign 15 miners to dig out a farming chamber, along with 10 new farmers and 10 haulers, who are to get dirt and loam from the cavern layers and bring it up to a place with no scary monsters, i.e., our chamber. A team of 5 engineers is to install electric floodlights to the farming chamber. Get our team of alchemists and haulers to use one-quarter tub of nitric acid to make mercury fulminate primer, to be stored in our explosives storage chamber. Our conscripts are going to be given gun safety lessons (Assume a gun is always loaded, never put your finger on the trigger unless you are ready to kill, never point your weapon at a fellow soldiers), as well as a rundown on what they will be handling, as well as basic military conduct, in classes to be taught by the administration and military leaders.
EDIT: Making an entirely new chamber is kind of a waste of time, so just:
Wall off a section in the cavern layer with 15 assigned stonecutters and 10 Haulers, do pull stone or carry dirt around.. Proceed to have 5 engineers install electric lighting to grow the crops.