Hognose are rear-fanged. But none of the pit. species. The open mouth thing is pretty much normal, but they don't have to do it to his. Not very wide, anyways. Usually they just open it a little bit, kinda side-ways looking.

I catch them alot around here (The bullsnake). From my experience, it's mostly just a big display. Maybe a bite or two initially, and some musking. Usually start calming down a bit after the initial display. If you take them out and are handling them, anyways. They like to hiss for a good 5 min. after you leave them alone. Gotta love em.