"The perpetrator would, at the very least, have a duty to remove himself from a situation where such heinous behaviour might continue and his confessor would have a sacred duty to inform him of this. "

But the point of the whole Clergy Sex Abuse crisis is that it was NOT done.  That is why the Catholic Church has mired itself in so much scandal.

If a confessor made absolution conditional on the perpetrator going to the police as having committed a terrible crime, then there would be no scandal.  But what happened (and happens) is that the perpetrator is 'forgiven' for having committed a sin, and allowed to continue.  If too many complaints come, then the perpetrator is moved to begin once more.  If a priest confessed to murder or to robbing a bank, his confessor would insist he give himself up to police.  Child abuse is just as serious a crime.  It murders the spirit and robs the child of trust.