I haven't had time to look at your demo in full, but from a quick look at the screenshots you sent, I think the problem is that you're trying to upload, in a single server call (Show File), more than one file.
Try splitting the uploads so that first you upload each file using a separate service which stores the file on the server (you could store it in a database table and return some Id of it), and then calls Show File to generate the document (it receives the Ids returned from the upload services rather then the actual files, retrieves the files from the database, generates the document, and deletes the file from the database).
Please try this and let me know if you encounter any additional problems.
I'll get back to you on the other issues later on.
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