are they making your labels? I'm thinking the person you need to talk to is the regulatory agency, the health district, the state food processors agency, those are the ones who dictate what needs to be on the label and how it needs to be laid out. Is a PO Box address OK, or does it have to be the physical address of the processing plant? or both?
Don't know anything about the co-packer, but usually it's something simple like what THP posted. HOWEVER, if left to the co-packer, why wouldn't they get as much info about their business on the label as they can?
Have you already done the product with the co-packer?