I added the web.config settings but there was no change that I could tell. I enabled logging for my account and compared internal and external log files. Both internally and externally it was seeing the hidden message and retrieving all of the policy settings. Externally, I kept seeing IsBrowserValid = False. I suspected perhaps compatibility problems with the browser at that point. Externally I was using IE 11. Internally IE 10. From the support matrix it says that EV is only supported in compatibility mode in IE 10 and IE 11. I know that I do not have compatibility mode on internally but it seems to work. Externally, once I added the our site to the compatibility sites list in IE 11, all of the EV buttons and functions appeared and seem to work.
The only outstanding issue I have now is that selecting anything related to the vault prompts you to log in to the vault. I'm not sure if you can pass-through authentication from the owa session to enterprise vault session. Internally this works fine because pc's are domain joined and use integrated windows authentication.