The first one about not seeing the wonum/siteid in the response you can get the primary keys back by enabling the system property mxe.int.keyresponse.
Regarding the action="Delete", that's something you could send in a message to delete the workorder (or if referenced on a child object, the child object on the workorder). It's not too common to do in integrations and there are a lot of business rules around work orders that would prevent deletion. For example, once a WO has been approved it cannot be deleted.