i don't understand. you've come asking for advice and you've had input from some of the best on this board. why are you so quick to dismiss them? who knows, he may have a combination of health and behaviour issues going on. aside from the aggressiveness, he sounds exactly like Loca after i first adopted her. besides her very tough behavioural issues (some of which linger), she has bee prone to tough-to-diagnose UTIs.
ETA: DarkHorse posted to ask for advice. if she posted about the behavioural problems she described, i bet everyone would be encouraging her to have his thyroid checked. that's exactly what she's doing. i also have to say that i think it's sooo unfair to suggest returning the dog every time somebody posts with a problem.