Here I'll put everything that I notice is worth highlighting, mostly small issues with Defcon or Visual Studio settings.
C:\Defcon\Defcon.exe. Command Arguments: Enter command line arguments here, for example ai=“AI/simplebot/simplebot.dll” host to automatically host a game, with the simplebot bot preselected. Working Directoy: Set this to the directory where Defcon.exe is, for example to ../../..