This researcher gives the birth date for Thomas as 05 April 1851.
Here again is the 1865 census we already posted for this family: 1865 Lyngens Tomas Tomassen age 48 born in Lyngen Bereth Andersdatter 48 born in Lyngen Ole A. Tomassen, their son, FISHERMAN, 21, born in Lyngen Tomas J. Tomassen 13 their son, born in Lyngen Nils H. Tomassen 6 born in Lyngen Anne M. Tomasdatter 19, helping her mother in housekeeping, born in Lyngen Inger K. Tomasdatter 16, helping her mother born in Lyngen Elen Malene Tomasdatter 11 born in Lyngen Bereth M. Andersdatter 65
Here again is the 1865 census from Horten posted above:
1865 Census in Horten Anne Thommas widow Thommasen, age 46, born in Skjeen Ingeborg Vilhermmine Thommasen 18, d [=datter/daughter; ug = ugift/unmarried] b Horten Anna Thommasen 15 d born inHorten Thommas Thommasen age 12 born in Horten Anders Thommasen age 5 born in Horten Hendrijette Augusta Thommasen 3 born in Horten
The Rootsweb discussion says Anne was married to Johan Thomassen. If this is correct, and if we stick to our guns and search for a father named Thomas Thomassen, then the family in Horten is ruled out.