Most of my games are hermit forts and this is... well, not that new challenge. Fun regardless! Although considering everyone else as enemy is a new twist to me. Once I locked out the rest 6 while the Urist McChosenOne continued living underground. Unhappy thoughts started to accumulate to the 6 and eventually few went mad and got themselves killed. However, few of them, and many of the immigrants actually seemed to survive indefinitely outside. But I blame the temperate environment that I chose. There were puddles of water and various small critters they consumed. Since merchants didn't have access to a trade depot, some got soon killed one way or the other, along with their pack mules. Eventually the fort surroundings become so cluttered with items that you are forced to abandon the game. Even if you organize things so that their deaths happen in orderly fashion, you will spent a great deal of time carrying the items around. So [SPEED:300] is very much recommended. Note that half of the time your hermit dwarf will spend standing around and figuring out what to do next, even if there's a ton of things to do. Maybe this is the problem? Idk.
Carrying one item at a time per dwarf is a severe limitation. And the lack of certain commodities may drive you to ragequit and start over. Also, if you don't want to personally kill the 6, pick an environment where there's little food, or a high number of predators outside. It's kinda shame that you can't control the dwarf directly...