Feed store birds are pretty much the same as hatchery birds. They're not carefully bred, and might not be pure bred at all. This site has an excellent comparison of hatchery bred birds vs commercially bred birds.
http://janickibuttercups.weebly.com/heritage-breeds.html
But what you can't see there is the temperament.
If you get Jersey Giants from a reliable breeder, it's
highly unlikely that you'd get an aggressive bird.
But if you get a hatchery bird, you're getting the genetic equivalent of a puppy mill dog.
Also, your rooster is 10 pounds or less? But the APA Standard of Perfection states that a Jersey Giant cock should be 13 pounds.
http://nationaljerseygiantclub.com/media/Document_22.pdf
That's a big difference.
And, their eggs aren't white.
I mean, I don't want to be argumentative, but I strongly suspect you've got birds that may be partly JG. But not pure JG.