The biggest whitetail I ever shot (200+ lbs) was with a 200 gr XTP. A complete pass thru @ 75 yds., double lung, and he only ran about 50 yds. My load was 80 gr of Pyro P.
And as johnmorris said, many a buffalo was shot with the .45-70 (and .45-90) using 400 - 500 gr bullets. I see no reason why a 65 gr charge of FFFg will not humanely kill a deer.
As for the 1000ftlb energy necessary - I say hogwash! I've killed deer with the diminutive .38-40 albeit at <50 yds and they did not go far after the shot. It all boils down to shot placement pure and simple. You plug the heart or both lungs and the animal will go down.