I just saw your thread now ~ you could have hijacked my thread- we are here to support each other!
As long as you and the parents are on the same page with how your handling things, it might just take time to get the little one to change his behavior.

Just a thought, today I had a little one cause another little one to cut and bleed. I didn't give the hitter any acknowledgement and went the the little one who was hurt and cuddled him. Then afterwards, told the hitter to say sorry and we don't use our hands to hitting.

Sounds like your little guy is still testing the waters. As long as parents and you are on board with the same thing, he will change. My own dd used to bite! It took a long time to change that behavior and I didn't let her get away with ANYTHING. It took time but she changed her ways.
Hang on...it will change, just keep doing it