The main issue here is why is the male the Alpha?

The answer is because you are not.

That is also the problem.

While it may seem OK for the dog to take control and the bitches to be submissive, where are you? Can you stop the dog? Are you expecting the bitches to work? (I can get why you are not so worried about certain neighbours!!!!!)

This either is an issue that you have work VERY hard on with a behaviourist that you trust or you have to put up with it (and see all of your dogs under stress every day***) or you get rid of the dog and work hard with the bitches.

*** All the dogs are under stress - they are looking for direction and "rules" from a leader. The male has assumed the role of leader because he can't see anyone else around that he can trust to do it right. He is a weak leader and has to resort to intimidation to get his followers to do what he wants them to do - hence the cowering of your bitches. The bitches do not want a weak leader, it is a natural state of affairs for any dog to be told what to do, when to do it, how to do it and to understand the consequences if they disobey. A weak leader makes them nervous, a strong leader brings peace and harmony. The bitches understand that the leader is incompetent and know that he will be harsh if they disobey or hesitate. The dog is in a constant emotional state of near panic whilst trying to show how cool he is on the outside - he knows that he is a bad leader. He has to use intimidation to get the bitches to obey him. He doesn't understand the human world he is living in so does not know what leadership decisions to make....it goes on and on and on and on.

These are working dogs by design - humans have bred them to do a job. They need to have mental activity much more than physical. They need physical activity they can make some sense of - it needs to fulfil the instinctive drives they experience. More than anythying they need a strong leader, you, to provide these things and participate.