Seeking Nils Olsen Balholm (1813-1896)

Hello -- I'm looking for info on the parents of a ggg grandfather, Nils Olsen Balholm. He was born 1813/1814, probably at the Balholm farm in Balestrand i Sogn; married Brithe Iversdatter Vikøren 13 Jun 1848 in Vik; and died 22 Feb 1896 at the Vikøren farm in Vik. I'm most interested in his parents or other ancestors. I've tried every source I can think of, including online databases, census records from 1801 forward, etc., but every one has been a strike-out. There is a bygdebok for Balestrand, but it apparently doesn't include any info on Balholm (it does touch a group of Bale farms, but I don't have any evidence that Balholm would be part of that group). Any help would be deeply appreciated. And of course I'm willing to share anything I have that might be of interest (including a small amt of family info on the 1904 S/S Norge sinking, which my father's paternal grandfather survived). Thanks much, Carter Nelsen Minneapolis