Prosecutions

If you are an attorney, is there a point where nonlegal moral considerations supersede your ethical commitment to your client? If you were a defense lawyer and your client was innocent, but you could not prove it, would you violate ethical barriers in service to your client?
Are the following actions of a prosecutor legal? Are they ethical? Explain your answers.
Authorizing the arrest of one brother for drugs (knowing the young man would lose a scholarship to college), even though the prosecutor knows the charge would be thrown out, in order to have leverage so that he would give evidence against his brother.
Announcing a suspect of a drive-by shooting to the media so that the offender is in danger from the rival gang members, and then offering protective custody only if the man will plead guilty.
Authorizing the arrest of a ten-year-old boy who confessed to a crime, even though there was no serious possibility that he was guilty, in order to pressure a relative to confess.