Barn might be useful. It provides some resource storage, and allows animal-based food production buildings as well as fields around it. Of course, if you're in the north as your -17°C weather implies, you're not likely to be able to buy the stuff to start producing animals. Straw has been absent from the market for weeks, save for the 250 units I just grabbed for an obscene price just now *maniacal laughter*.
It might also help to plow now, so that you have fields set up for when the temperature rises and can start getting crops produced. Also note that vegetable gardens can produce Cabbage/Carrots/Leeks/Onions at -5° instead of at 0° for fields(0° is required for onions, and 10° for flowers and garlic, though).
My school is done, men are being trained, and soon I shall have enough money to buy the billion nails needed for a wooden fortress. Are there any must-train jobs? I'm getting a surveyor, a quarreler, and a wood cutter.
"Quarreler"? I'm guessing a quarrier? Odd that Chrome's spellcheck says quarreler is right and quarrier is wrong despite Dictionary.com saying its the other way around("quarreler" redirects to "quarrel", as in, a fight).
Besides that, you will want a construction team consisting of a carpenter, bricklayer, and a roofer. While there's overlap between the carpenter and roofer, the extra guy and skill will make construction far easier - and the carpenter lacks the roofing skill. For some constructions, a digger(requires clay/clay pit) might be useful. The surveyor probably isn't that useful and is effectively obsoleted by the architect.