Another update. I went and looked at the ProductThumb column, and all the fields are blank. Same as the ProductImage fields.
I then went to look at the Insert Record (products) on the admin products_insert.php page, and found that the ProductImage column has a type of "Text", and a value of "<?php echo ($WA_DFP_UploadStatus["WA_UploadResult1"]["serverFileName"]); ?>" . The ProductThumb has a type of "text" and a blank value.
So I figured out how to get the insert and update field to post the filename to the database. The correct valuefor the ProductThumb column in the bindings tab for the Insert Record (products) server behavior is: "<?php echo $WA_DFP_UploadStatus["WA_UploadResult7"]["WA_UploadResult7_2"]["serverFileName"]; ?>". This was the "Server File Name" binding with the images folder path before it. So the binding said ../product_images/thumb/[FileName]_thumb (61): Server File Name.