That timeline has troubled me in many ways, but the one nagging question... Floyd went into hiding in June, 1973, after failing to make a court appearance (for an assault on a young woman right after being released from prison/parole). Of course, considering the circles within which Floyd operated by that time, Sharon may have been abducted by someone else years earlier then given (or taken) in turn by Floyd.
So... Sharon should have been old enough at that point (in late 1973, 1974 she was most likely between 4 and 6 years old) to have remembered her mother. Why didn't she ever tell anyone about her? She mentioned to friends and teachers that her mother was killed in an accident, but I feel it most likely that this is what she was told to say by Floyd.