USCIS allows the mailing address to be a P.O Box or other secure address, especially for VAWA petitions where safety is a concern. USCIS wants your physical address as well. USCIS does not automatically treat a P.O. Box as your protected confidential physical location.
If you are filing only Form I-360 without Form I-485, you cannot request an EAD at this time, so you should mark "No"
You can continue using the same P.O. Box even if you move to another neighborhood, city, or state, as long as the P.O. Box remains active and you have access to it. But if your physical residential address changes, you must update USCIS.