J.W.
Here is the thing, I am ADD my ex is most likely PDD or Asperger. The only diagnosis he has received is ADD but that doesn't explain most of his most annoying traits.
Like your number one, I and most people I know with ADD are some of the most social creatures on earth. Not my ex, he prefers home.
One of the biggest things about my ex is he denies our son's diagnosis. He will not consider it, mention it, it doesn't exist because it is looking in a mirror for him and he refuses to believe he has the same issues. So if Andy is fine, he is fine.
I guess I am saying since they overlap, ADD and PDD, you need to look at where he diverges which is the social issues, that is why I would put my bet on PDD or another autism spectrum disorder.