It would seem that he has FAE fetal alcohol effect. There are hundreds of effects of alcohol use by mother while child in the womb and it is felt that father's alcohol use may impact as well. He does seem to have physical things such as the short stature , impulse control, and the thick glasses.
But he could have issues because of growing up in an alcoholic home and the resulting chaos as well.
I bring this up as people with FAS or FAE are not brilliant in the way they carry on their life. It is so unreal that he eluded being captured for anything for so many years.