How can I fix conflictions with IIS Enviroment as well as overall security?

I have wordpress installed with a custom theme built.Everything we have is well protected behind our firewall as well as two dell Secureworks appliances that monitor everything and we have a Fortinet Webapp that handles all traffic.
Overall security is the primary reason I'm running into as it appears that the solution that are most offered on the web is leave the world wide open (777) which we haven’t done knowingly. Wordpress appears to give me a lot of issues with permissions with the application itself. All our issues have been related to it running in an IIS environment. Can you please help me?