The other birthdates I have for Ole are - from 1880 census, Ole A Dahl reported he was 40 yrs old, making an 1840 date possible. His headstone says merely "1843" (He actually has an older headstone that I have a picture of somewhere.)The One World Tree has Jan 22, 1843 that was user-submitted.I suspect this date was supplied by Olie Henderson Dahl, since the headstone is also spelled this way. Albert's birthdate is listed as Oct 9, 1871 and born in Christiana, Norway. I am going to continue to search down the family tree, through the other children of Ole & Mattie Lula Dahl, but I think we would already have the missing information, had it been previously available through these links, but I know this is not certain.
Also, is there a place called "Norrough" or maybe "Norvergh" that you are aware of? It appears in the 1880 census the census-taker wrote "Norrough" as Ole's place of birth, rather than just Norway, while his parents were both explicitly written "Norway".