1000 foot pounds of energy for whitetail is a bit over for the deer around here. I've killed them with a lot less!
My farthest kill with a 94 Winchester and a .30/30 is 135 yards. Broke both front shoulders and he dropped right there. That was with factory irons. I'd be comfortable out to 150 yards or a bit more with a good aperature rear sight. If I was using a bolt or single shot rifle with a scope, I would be confident at 200 or a bit more.