I think the standard approach in this situation is to write a function that will evaluate your complex criteria and return a value that you can use in a simple predicate. So in your case, write a function that will evaluate the 3 aspects (SDDELN=0, SDNXTR between '530' and '999', SDSHPN>0) and return a value of, say, 1 if all 3 are true. Then you can provide a simplified predicate for the audit_condition in your DBMS_FGA.ADD_POLICY.
audit_condition => 'mypkg.myfunc = 1'
Mad Dog Morgan provides an excellent example...