Just a quick reply before leaving for work;

1. For what purposes are your story characters tanning furs? To be traded for fogeign goods? To make winter clothes for own use? To make leather for various tools etc? I guess all that kind of matters affect the preffered method of tanning. I'm not expert on the issue, but I know people who have been doing it (and actually I'd like to try it this winter), so I hope that with some time and asking my friends I can find a detailed answer =)

2. quickly: a skilled (wo)man armed with a good axe could build a simple log house all alone.

3. my sheep are indeed finnsheep breed. I don't shear them in the autumn, so with their natural wool they survive the winter in their shelter. They have a roof and three walls, with dry straw on the ground. Cold is not an issue for them, as long as they stay dry and protected from wind.