You should probably create the template document in MS Word, insert comboboxes where you need them.
Then you can use Aspose.Word FormFields and FormField classes to access and modify comboboxes and their values programmatically. So you can load your database values into the document.
Note you cannot use Aspose.Word to present the document to the user. Aspose.Word is a non-graphical component. You need the user to open the document in MS Word.
When the user selected values in the comboboxes, you can use Aspose.Word again to open the document and retrieve values from FormField objects and store in the database.
Comboboxes in a Word document can only store one value, they cannot store key-value pairs. If you need to store a map of key-value pairs somewhere hidden in a document you can use Document.Variables or Document.CustomDocumentProperties collections.