Hi,
There is a huge amount of open ended possibles... lots of details would be needed... but a place to start would be:
The AppID is for SAML and OAuth... test without.
I wouldn't set proxy at all.
Test in Chrome or IE 11
Id make sure IIS is running properly on your web server, test by enabling anonymous.
This is definitely an architectural issue..
Since the Web application works when developing (Web Application builder).... downloading the zip.. unzip and.. dump to wwwroot.. find the folder in IIS... 'Add Application' ... just as a test.. should work...
then start applying sercurity and such to see where the breakdown is in your setup.