Well, wow I took the time to download that file and watch it - BIG file - LOL!
What I saw was a young dog with good tug instincts - he really liked the tug and didn't want to give it up. It is someplace to start with any dog you want to train in a sport - they have to have the desire to play.
What I found more interesting was the converstation going on - could not get all of it, but got the name Top flight K-9, $1200 for a puppy UP FRONT before the litter is even born apparently. I thought that was interesting as I don't know of any breeder that would ask for the full price up front. The person talking said he had a waiting list. I'd be interested in knowing more about where your dog came from and his pedigree.
I think it is wonderful that you train with your dogs. I like to see people doing stuff with their dogs - whatever that might be............. and there are so many possibilities out there. While schutzhund is not my thing, I am interested in it. I do conformation/obedience/rally/Therapy Dog work with my Dobes. The proper temperament is so critical in any sport - you can really see the difference in a Doberman that is solid and one who is not.
I do think that the male and male thing could present a real problem. The two seem like they are pretty close in age and that is not a good thing. You can be as alpha as you want to be, and the aggression may still happen. I hope it can be controled, but I would not want to bet on it.
I also want to comment on the Schutzhund III/Breeding thing. While I do want to see titles on Dobermans and think that is a great thing, I also know that there are dogs out there with good temperaments and who with good training are perfectly capable of titling up to the Schutzhund III..........but they are still not breed worthy. There is more to it than the titling when you are looking at breeding. First and foremost, they need to meet the breed standard very closely - there is a reason for the standard. Proper temperament is included in the standard as it is such a part of the breed itself. Then there is health. Dobermans have several serious health issues, and while health testing cannot guarantee good health, it certainly should never be ignored. Pedigrees are also a key factor in breeding - knowing what is behind your dog is so important. Heredity and genetics always have to be considered.
If we are to strive for the total Doberman, all things must be looked at - not just one to the exclusion of all others.
I hope you stick around and enjoy the forum. There are many interesting people here, and we have a really diverse group that do just about everything you can do with Dogs!