As far as I can make it out you seem to have the right attitude here. You need to be aware of the potential problems this animal may bring and the most difficult part of that is to KEEP it at the forefront of your mind week after week.

My first concern would be a neurological problem. Has a vet tested his reflex actions and his eyes? If not it would be worth a check up.

Secondly what makes this type of dog dangerous when things go wrong is not the fact that they become aggressive but the lack of warning that full scale aggression is about to happen. You do not get a chance to divert or avoid.

I would be very very concerned to have a fourteen week pup behaving like an adult. If he really is then he missing vital learning stages of his development and specialist training may be the order of the day. (I have come across three pups that really did not have any puppy behaviour-each one had been orphaned very early in life and raised to around 7-9weeks ( if I remember correctly one was 16 weeks) in isolation from other dogs.)

I suggest you ask another trainer for a second opinion on the pups behaviour and get a vet's opinion too. Also ask your trainer to be a little more specific in her concerns. What behaviours are missing? Why is the level or type of aggression unusual?

Let us know what they say and we will have a better idea of what we are really dealing with, good luck.