I'll preface this by saying my interview was 2 years ago almost to the day, so things may have changed, but I am an interview ambassador (i give the tours to interviewees), and I haven't heard any negative results in talking to the interviewees. Maybe some of the MSI's can add something to this (after they're first neuro exam tuesday).
I wouldnt worry too much about the random ethical questions you hear horror stories about. I would definitely recommend knowing your personal statements foreward and backward, and be ready to elaborate on them. One of the things that drew me to Western was that I got the impression in my interview that they actually wanted to get to know me, and didn't seem to care too much about my stats during the interview; I got no questions from Western about why I got score X in verbal like some other interviews I had. Your stats are competitive, and that's why they've invited you for the interview; focus now on why you want to be a doc, and what drew you to osteopathic. As far as history of osteopathy and western, I didn't know anything other the bare minimum when I interviewed, and I don't think it even came up. (one of the first lectures you get first year in OMM class is about history of osteopathy and history of osteopathy in california specifically anyway) Most importantly, be yourself, be honest, and enjoy yourself. Good luck!