You may be better off getting a behaviourist involved at this point. Mals can be a tough breed (at least that's my understanding). If you know your dog is already under-socialized, you need to get something on the go and quick or you will have a bigger problem on your hands.
It's not an option to give up on the training. In my opinion, training is a life long event - we should always be doing it with our dogs.
Please don't go back to this training/obedience class. It's sound all very dominance/alpha theory based - it has the potential to make matters worse for your dog.