1. The headbutt was intentional. It was the heat of the moment type of thing. Ortiz is a fighter, Floyd is a boxer. It was Dirty. Probably payback for the elbows he ate, and the holding of the head, but still dirty and illegal.
2. Floyd took a cheap shot that should NOT have been legal. When the ref stops a fight, he has to resume the fight. The ref did not resume the fight, and was looking towards the judges table. When Floyd hit Ortiz, Ortiz looked at Cortez. Thinking "how is that legal?". Then Floyd hit Ortiz again and knocked him out. Cortez, known to favor Floyd in most of his fights, stopped the fight.
He never started the fight again. This is the first time I have ever seen a boxing match where a ref stops the fight, then a fighter starts it back up himself, without the ref starting it again.