Can anyone validate that A1 K9 Rescue (www.a1k9rescue.com) is a valid rescue group and not a puppy mill?

Not a valid rescue group- note that it doesn't say anywhere that they are 501(c)(3) tax exempt. These people BUY dogs (primarily young puppies and often whole litters or heavily pregnant females) from puppy mills and re-sell them to 'get them out of breeding'. They require them to be spayed/neutered. BUT, they are putting money into the hands of the people that bred them. And those people just buy OTHER dogs with that money and subject them to the same misery. They are basically brokers- the only thing that separates them from any other puppy mill brokers is their spay/neuter requirement. Real rescues have primarily adults and seniors, and occasionally some puppies or a pregnant female. They don't have almost exclusively young, marketable puppies.