It's definately NOT a dog. no claw marks. look at the left digit of the paw print and notice the defined edge on the surface of the snow. absolutely no clue as to a claw. you will see claw marks on dog prints. Any measure on the intergroup size or spread of the track?
Other indicators to me are the size of the track from your description and the lack of a concave arch on the base of the pad. Also since they are pretty aged it's tough to tell but you can make out a double-lobe on the top of the central pad - that indicates a cat family creature.

I'm going with cougar for sure.