Keep in mind that rabies is pretty prevalent in the area, Usually at least one or two foxes a year show up on the farm with it. So not just with this fox, but with others, as well as raccoon and possum are definitely something to steer clear of or keep an eye on. Currently have a mother fox with pups living in the woods behind the house, fortunately they're all healthy and react the appropriate way when they encounter a person. The fact it ran off when you opened the door is a good thing.
I agree. It looked alert, functional, and not zombified at all. Could you smell it? The really mangey foxes I've encountered had a strong and distinct (and bad) smell. Honestly, it didn't look that mangey to me in the video...just not as red and fluffy as the Hallmark card ones. Unless you have chickens or bunnies, I don't think it's a threat. I wouldn't suggest trying to interact with it (or letting your dogs). In addition to the mange and rabies concerns, it is still a wild animal (with teeth) and should remain that way.
If you haven't experienced it yet, they make positively horrific sounds, especially at night.