Actually, making a fool proof self-sustaining fort is not that difficult, to be honest, especially if it only has to survive a year. You can technically just dig in and wall yourself in, set up a few farms (you need surprisingly few crops to feed your dwarves) and breweries, train a few craftdwarves and the only thing that can kill you at that point is a very unlucky special mood (dwarf that is struck with inspiraion to create a legendary artifact, but if they can't get the resources to make it, they might go berserk) that goes into a death spiral (a killed dwarf causes another to have an outburst of anger, killing another, which makes another start brawling etc), but even those can be managed.

And then, you can just automate most tasks so it runs itself indefinitely.