It is possible that 1870 census "William R." is "William K."Interpretation of old handwriting can be incorrect. Check the microfilm yourself, if possible.
Surname variations are: Elsemore, Ellsmore, Elsmore, Ellsmor. If you request a search, have all variations checked.
Before 1892, vital records were kept by town clerks. Births records before 1828 in the Calais area are tough to find. You could try: Calais City Clerk, 5 Church St, Calais, ME 04619-1603. Phone:(207) 454-2521.
Other resources: Vital Records of Calais, Maine to the Year 1892. Compiled by Sharon L. Howland. [Rockport, ME: Picton Press] published 1998. Has every name index.
The Calais Free Library, Union St., Calais, Maine 04619; phone:207-454-2758.
A microfilm of the original Calais, Maine Vital Records book, 1839-1911 can be ordered for viewing from a LDS Family History Center.