I'm not sure what's going on with your Beersmith, but when I put in just the Chinook FWH, I get 73.9 IBU just from those without the other additions. Not sure what setting you're using, but something's wrong in your Beersmith, not in the recipe.
Currently On Draft: Bamberger Rauch Dunkel, Belgian Blond, Pilsener Urquell clone, Smoked Porter
Bottled: Concord Pyment, Mi'Apa Sparkling Mead, Chimay Blue, Old Simcoe American Barleywine, Old Cantankerous
Fermenting and Conditioning: Pseudo-Decoction Munich Dunkel, Left Hook Bitter
Recently Kicked Kegs: Fresh Hop Pale Ale, Citra Rye IPA
On Deck: Old Rasputin, Northstar IPA, Ur-bock Dunkel