Adopted Dog Appears Abused

Question
Here are some details on the 3.5 year old lab we just adopted:
1.  He has become very attached to my wife and never leaves her side.
2.  He has severe apprehension and skittishness around both me and my daughter's boyfriend even though we both have lots of experience with dogs.  He is not this way with either of my daughters.
3.  Whenever someone moves their hand or is behind him, he will flinch and quickly move 10-15 feet away.
4.  I offer him treats and he will approach but then backs away slowly.  He will not let a male walk up to him.
5.  Now he will growl and bark if I enter a room as if he is trying to protect my wife.
6.  He definitely has issues that we are trying to work through but so far our biggest concern is that it is difficult for him to adjust to males.   He is a beautiful lab and it is upsetting that he has this apprehensive nature around other people.   So far he seems like a one person dog and not like a typical Labrador retriever.  Do you think that this behavior will change?  We are thinking that this lab came from an abusive home environment but have zero history.  

Answer
Your dog has an acquired fear response to male humans and a conditioned fear response to being approached head on and to sudden hand movements, most likely the result of physical, psychological and emotional abuse.

You cannot expect this dog to rehabilitate for some months.  I suggest you hire a certified applied animal behaviorist with expertise in treating acquired fear aggression and rehabilitating behaviors acquired because of abuse and neglect.  Call the veterinary college in your geographical area and ask for referral to a Ph.D. or DVM.  Do NOT trust dog trainers, they simply do not have the experience (for the most part.)  Because this dog is bonding to your wife (finds her a source of comfort, and god knows he deserves one) he appears to be developing aggression and that is why you require an expert to do in person evaluation, observe his behavior, and educate you on how to rehabilitate him.  This is NOT a quick fix and no amount of posting on any internet site is going to help this dog.