I did an export of your data (a single table called Validators_Boundaries) to a file called VB.QVD. Then I made a new model with some listboxes, and a script that does two things:
1. Load the SA INLINE table (missing from your example qvw) with the code from your comment immediately above mine.
2. Perform a LOAD of VB.QVD
Enabled both "Initial Data Reduction Based on Section Access" and "Strict Exclusion".
This model works without a problem. See the attachment, this one has a disabled SA. To test it yourself, make a copy of this file (like "TestSA Secured.qvw") enter the script and remove the comment markers from the first line. Reload, save the qvw, restart QV and load the new file. Use the above credentials (in UPPER CASE) to enter the newly secured model.
You didn't forget to put Section Application; somewhere in your original script by any chance?
Remember, Section access tables won't show up in your document. They will grant/refuse access, reduce data if needed, manage initial selections and so on. But you will never see a table containing usernames and passwords.
"...but still not loading any data at all..." What exactly is happening in your document? Is everything reduced away?