Hello Chad,
In this case, you need to create a custom action. OOTB we only ship example for Incident table. But you can copy the action and mimic the same logic for Requested item table.
In case of Ebonding example for the incident table, PayloadBuilder is the script include which builds a payload by reading a set of fields from an incident table and uses it in the REST steps. Go through it for reference and create your own script include for the use case you have.
To answer your second question, we don't create a record in reference table if the value doesn't match. Forex: If the source incident details assignment group doesn't match with target instance, then we set the assignment group value to blank when a target incident record is created.
Please let me know if you have any questions.
