I think Bernard is a host clone of the original Arnold. That is why Bernard couldn't see Arnold in the photograph that Ford shows him - he's programmed not to see things that would break his reality. Bernard originally thought the clone of Ford's father was Arnold - because he was the only other one in the picture.

I also think the scenes of Bernard interviewing Dolores are actually in the past, except Bernard is actually Arnold when he was alive in those scenes. His interviews of Dolores are part of Arnold's experiments on making the host's more human.

Host Delores may even be a clone of someone that was important in Arnold's life (wife perhaps). The backstory of Bernard's sick child is a substitute for the real tragedy of Arnold losing his wife...