Is he neutered? That's a first step, if he isn't, but in any case, I think he needs to be "re-trained." Maybe a basic obedience and socialization class is in order, now that he is a "grown-up." (Yes, bigger dogs do take a lot longer to mature!) The construction could certainly be upsetting him, and making him feel more territorial, you need to establish with him that YOU are the Alpha dog, not he, and YOU will make sure the house and property are safe ....