Of course he knew there were allegations. (important to note that they were only allegations at this point) That doesn't mean he knew there was actual abuse. I would think anyone in his shoes would be skeptical, given the way he received the complaint, and given the fact a district attorney didn't press charges against Sandusky after investigating previous allegations/complaints.
That isn't his job to determine if there was or wasn't. He reported the allegations to his superiors. Once he did that, only holding the position of Head football coach, with no official supervisory position over Sandusky, as he was not working under Paterno in 2001, he pretty much did enough that would clear him of any criminal wrongdoing. It's not like he was employed in an administrative position.
What would you charge him with?
From a legal perspective, It's irrelevant what he persuaded others to do. That's on them for allowing themselves to be persuaded. Joe Paterno wasn't the boss. He doesn't get to make that determination.