Unfortunately, I haven't yet studied how a sin gets to be on the major list, so I can't help you there. I will check through my book of shafi'i fiqh when I have a chance and see if there is something there.
All major and minor sins are in some way based on the Qur'an and the sunnah (example of the Prophet), whether it is explicitly mentioned, or implied. Some sins are infered through qiyas, analogy. For example, smoking cigarettes. It's not explicitly stated anywhere in the 2 major sources. But, scholars look at the basic islamic principles - that one should not do physical harm to one's body on purpose - and analogize that smoking causes great physical harm, and as such, is either forbidden or makruh.
The beard issue is something of great importance to hanafis, particularly those of the subcontinent (pakistan and india). One may even say they obsess about it. While it's important to other muslims, they don't take it quite as obsesssively as the hanafis do
This is a fatwa that may be of interest on the issue.
As for keeping a dog, there are two hadith that are the foundation for the ruling on not keeping a dog as a pet indoors beyond whether or not their saliva is impure (and you are correct, according to the malikis, the salivia of every living creature is pure):
It is related by Abu Huraira (ra) that the Prophet (saws) said, "Whoever acquires a dog, with the exception of a dog for hunting, or guarding sheep, or protecting the harvest, then a large portion of his reward will be diminished every day." [Reported by Bukhari and Muslim]
Abu Talha relates (ra), that the Prophet (saws) said, "The angels do not enter a house that has a dog or a picture." [Reported by Bukhari and Muslim]
My egyptian husband is not a dog person, and will shrink from dogs touching him. His brother, however, keeps several dogs at home. I would venture to guess that it isn't a sin to keep a dog, but that it's definately not recommended, ie your reward is diminished and you don't get angels hanging out at your place.
If you're aware of the consequences and are ok with them, then all's well.
As for living in Lapland, there is a portion of fiqh that deals with urf, local customs. The local culture and customs can influence how the Qur'an and Sunnah are interpreted. Now, I'm just speculating here, and I am less than a student (ie I haven't begun any formal studies of fiqh), but it could be conceivable that since keeping a dog outside is impractical, but that you still needed it to guard you, then perhaps it would move from not recommended to neutral. Now, that's purely speculation on my part and should not be considered a fatwa in any way, shape or form