I'll add a few doodads here as I come over them, for anyone who might be interested.

The nisse is in fact remains of a kind of ancestor worship (I had no idea). He was also called "haugbonde", which means "mound farmer".
In this context farmer is more correctly translated to just "man", or "free man". Just about everybody lived on farms, but the head of the household was "The Farmer", i.e. he was not a servant (or nobility), or a craftsman. A "storbonde", or great farmer was pretty much a minor king of his region.

Anyway. The first owner of the farm, the first settler, was buried beneath a mound on the farm when he died, and presumed to hang around the settlement thereafter. It was common to sacrifice a little beer by the mound, and in general try to stay on his good side

Other remains of the harvest worship: Norwegians still hang up sheaves of oats around Christmastime, for the birds to eat, and decorate by the door with a large goat-figure made of sheaves of oats.

Christianity was definitely forced through by the sword, but I think they were pretty flexible and laid-back about integrating it with existing customs