The 1914 date did not come from Russell. Barbour borrowed the date from earlier writers, all of whom were British Millenarians, often Anglicans. The same is true of 1874 which was looked to by others since the 1830s. 1914 was 'shared' by some Advent Christians.
I see Russell as a "True" believer, even if he was truly wrong. 1925 seems to be unique to the Watch Tower. Rutherford's reaction to the failure seems to mark him as fully convinced. F. W. Franz played with a date in the mid 1970s from the 1940s on. He was a fruit cake, but he appears to have believed his own propaganda.