The marks and cuts would concern me. I don't know if how he acts around the BO would be indicative of anything or not. I have 3 foals here who are almost 6 months old, I bred their mothers, bred them and have handled them since they were born. They STILL sometimes act like they think I'm there to eat them and try to run away and/or hide behind things and I can tell you for SURE they have never once been hit. So.........the jury is out still on that part of the 'abuse' story. If he's got clean line cuts all over, I'd be looking for something sharp, not a whip.