Citizens need a source of food and warmth to survive. Since the Help Menu states that citzens will only visit the nearest storage barn to collect resource then you can't depend on citizens going to your primary settlement to get resources. Even if they do take the long walk back to your primary settlement they will be wasting a lot of time doing so.
Your best bet would be set-up a Market near the offshoot settlement to ensure all the goods the citizens need are close by. Market Vendors will gather resources from Storage Barns and Stockpiles all over the map, so it'll ensure that citizens will always have the resources they require near by. The long travel time between the Market and your primary settlement could still cause some problems though, so you may need to put several vendors in the Market to ensure the Market always has a sufficent number of supplies.
Another option would be to build a gatheres hut, forester and woodcutter. The gathers hut combined with the foreseter replanting trees should ensure they have enough food. The woodcutter and logs provided by the forester should ensure they have enough fuel to keep warm. I suspet they won't have access to clothes with this method, but that will just decrease their productivity. So long as their homes are warm they won't die they should just work less and spend more time indoors where it's warm.
Managing population fluctuations, both local and city-wide, is one of the biggest challenges of Banished. But with the right technique, it isn't one which can't be overcome.
When you need some household to migrate to another location, build a new house for them in the new location and just before the new house is finished, order their old house to get removed. They will then become homeless and migrate to the new house the moment it is finished.
Single households are in fact quite handy in this regard, because they give you a higher flexibility (you can move a single worker and don't have to move two at the same time). The downside is, of course, that more houses require more resources to build and more fuel to keep warm.
As a result of population fluctuations you will soon notice that workers who used to live close to their jobs will switch jobs and have suddenly a new job which is far more remote. To solve this issue you should regularly (every couple years) unassign all jobs by making everyone laborers and then reassign the desired number of workers to each occupation, starting with those where you consider proximity most critical. When you add a worker to an occupation, the laborer closest to an open job of that occupation will be converted, so by reassigning regularly you can re-optimize who does which job.
Best Answer
Iron (and coal and stone and wood) do not go in storage barns. They go in the open-air stockpiles. You're probably best off just building sufficient stockpile space next to your mine. Use your markets to get the materials disbursed throughout the map.
Disbursing stone, however, through your town is actually a little problematic. Marketplace vendors don't pull stone to the markets so it will always just end up in the stockpile next to your quarry or trading post. Not much you can do about this.