I belonged to the New England Historic and Genealogical Society in Boston for a few years. They have the Maine VR on microfilm. I also went to the Mass. Registry. They let you do your own research in the current records.
I have no idea why the surnames are different. Just a theory that Oliver's mother's maiden or married name at the time of his birth was Abbott, but his father was actually William Page.
The Pages were in Bangor/Brewer from forever until 1882, then again from 1903 or so until 1919. Thus the tie to the area.