[JoeyP]

Okay there are a few issues here
The most important and the one you have to deal with rift away is that you have an aggression issue with your young guy there
The guarding and the growling have to be stopped immediately

Toys and food are never left around for him to guard
And any aggressive behavior has to be stopped before it escalates
He growls?..... He's put out of the room
He acts aggressively to the other dog or to you? Same thing

It's the speed and the force you use to stop this and the fact that you never let it slip that will stop this from getting worse