Your problem: In that period of time, the "surname" of persons in Scandinavia was NOT a surname as we know it. The naming system of Patronymics was in effect. For example, you quote a name of "Isaac Zachariasson Stalnacke." When he was born, he received a "given" name of Isaac. His second name, "Zachariasson" was the name of his father, "Zacharias" and the added "son," meaning son of Zacharias. Then, because there were so many Ole Olsen, Magnus Magnussen, etc., they were given a third name. This name was usually their address, their farm name. Stalnacke (Stålnacke) could have been the farm name, sometimes the name of the parish, or community. Anyone having that "address" may not have been related to any of the others. My Swedish ancestors name was Magnus Eriksson Byström, meaning a farm by the stream.
Once a Stålnacke moved from Sweden to Finland or Norway, then that name was changed to their new address. But, some did not, but that was very rare. To find such a name in Norway, as below, does not mean they were related.
Here is a Johan Stålnak in the Altens Parish in the Finnmark Fylke (similar to our Counties but different) in the 1865 Census. He is living on the Transfarelven Midstrand Farm.http://digitalarkivet.uib.no/cgi-win/WebCens.exe?slag=visbas...
He is age 54 was born in Sweden and is married to Elen Saraksdatter born in this parish. They have a son Johan Johansen, age 2 (The age of persons are based on what age they would be in 1866).
The problem, those persons with the surname of Stålnak/Stalnake/etc. are NOT necessarily of blood lines, but simply were born in the same area.
Click on Readings, Norwegian surnames:http://www.nndata.no/home/jborgos/jborgose.htm