The heart of the issue is that you cannot do this using the Dreamweaver insert record behavior.
The Dreamweaver insert record behavior is limited in that it will only allow you to store form information in the database.
When a file is uploaded, the file field does not actually send a value, it sends the bits of the file.
The digital file pro Upload File behavior takes these bits and recreates the file on the server.
Once the file is created on the server, a php variable is created that contains the Server File Name.
You need to use the DataAssist insert record behavior to be able to use the Server File name variabel when inserting the record.
See the "How to apply Digital File Pro to DataAssist Insert and Update pages " tutorial in the how to section of the Digital File pro support page: