When the brother takes down the New Orleans phone number from the card, he only writes the 7 digits without the area code. When he later dials (from Mississippi) he only dials 7 digits. A long distance call to New Orleans would require dialing the 10 digit number with area code.
Parker allows the electrician to remain in the evidence room unsupervised. In addition to what took place, this would have tainted the evidence in the room, making its use in a trial more difficult.
The chief tells Sweet not to pursue the red car since he did not want any innocent people hurt by a police chase. Since the occupant had fired a weapon into an occupied dwelling, this would have justified an immediate police response to apprehend them in the event they did the same thing somewhere else. It would also have allowed for the immediate apprehension of the suspect.