I am having some issues with my new puppy that I would appreciate some feedback on. I picked up my puppy at 8 weeks of age on July 31 from a breeder that breeds working Rotts from great bloodlines. I got two of the Leerburg DVD's and have spent countless hours reading this forum(which my wife is not happy with) because I just want to do everything right with my new dog. So far he has been a great dog and training has been good. I am trying not to rush things and have been mainly working on the sit(which he has mastered) and the come, as well as come tug games a little.
My first issue is that even at three months of age he shows alot of aggression. At 8 weeks when I brought him home he flat out fiercly attacked our other two dogs(boxer and Manchester terrier) that are/were bigger than him at the time. As of this writing he is 45 pounds already. A few weeks ago my wife went to scoot his food bowl more under him while he was eating because he was making a mess and he started growling and snapping at her. From what I have read in the article on this forum that dogs normally are not this aggressive this young. He also likes to try to dominate my 4 year old by nipping at him. Any input?
Second, what kind of correction at this young age should I be giving him? All three of our dogs stay in separate crates in different rooms of the house. Occasionaly their paths cross when doing their duty. When they do my Rott takes off after them. That is when the come command is not working. I am trying to lease train him a bit(with a fight). One thing about him is when I do scold him(usually by grabbing him by the scruff or popping the leash)he screams and urinates and acts as I am beating him to death.
Then he snaps at me(I am a bodybuilder/powerlifter thats pretty wired from the supplements I take and can have a short fuse at times) and I have made the mistake of fighting him a couple of times by stringing him up on the lease. Looking back and reading the forum I know i was wrong by getting emotionally involved in the fight.
Other than these concerns he is a great dog. Ever since I brought him home he has impressed me with his drive when I break out the prey toys be barking and lunging at them.
Please direct me I have made any mistakes or with suggestions.

Every decent Rott that I had was a pain in the butt at this age, and every decent dog I have had was/is a pain in the butt at this age. The nipping at the kid to show dominance? You need to describe that a little better. Most puppies at this age nip at running children, so more info is necessary. The running after the other dogs aggressively needs to be settled now. I would get Ed's dominant dog collar, and read up on how to use it effectively. If it is not a settled issue then you won't have other dogs in another year or so, and the wife will hate you and the dog.

What is it that you want to do with this dog?

The nipping with my son is like you said, when running. Also, when my son is on the floor or sofa watching T.V. the puppy stands or sits on my son and nips at him.
I have had dogs all my life including the ones before mentioned and a Doberman that stay primarily in the yard. Although we live in a rural area we got broken into about 21/2 years ago. That's when I got the Doberman. The Doberman even though he makes his presence known is a push over. We have a couple of acres that is fenced in that the Doberman lets everyone in and licks them on the way to the front door. My Doberman is smart, was obedience trained, and had some bite and protection training, but just does not have it in him.
We are from Montana, but right now because of job situations we have been here in Florida for awhile now working. I am in Montana often trying to keep the place up, so my wife stays here. I wanted a dog that will stand it's ground if need be. I am not looking to produce a junkyard dog or an attack dog, just a well rounded protection dog and companion. I did alot of research on bloodlines before buying my Rott. His mother is the granddaughter of Igor von
Muthmannsdorf(supposedly the greatest French ring dog ever)?
His father's side is all German bloodlines that all have Sch
III titles. So, I figured I got a decent dog for training.

Igor never did french ring. But did produce some nice dogs. As far as your problem with the child, I would just avoid the whole thing and have carefully supervised times where they can be together. Rott Puppies tend to start figuring where they are in the pack a bit sooner for the most part than other breeds. I always did as much as possible when they were young to kind of get it in their heads what a good deal training is, and that helped with dominence problems that cropped up. Rotts tend to go along good when they get who is in charge, otherwise they tend to be a pain in the butt, always doing stupid dominance crap while you are trying to train, and then you always want to choke the life out of them for continually doing so. One of the reasons I got out of the breed.