Accessing resources on localhost using domain credentials

I'm trying to set up Team Foundation Server 2010, Sharepoint Server 2010 and Report Server 2008R2. I apologize for how long my question/problem is but I'm really lost on where to even look so am being as descriptive as possible in hopes that I'm making sense.

The goal: Since developers can be inside or outside the firewall there needs to be a single http point of entry to TFS that works regardless of which side of the firewall you are and needs to work with external access to SharePoint and Report Server. Meaning we have it set up in DNS so buildserver.mydomain.com: points to the build service box which contains all of the services listed at the top of this post and specific services are defined/located by the port number. This is working great on every machine inside and out except for from the build server itself. All services must be able to work using external URLs.

If I use http:// buildserver.mydomain.com:4800/tfs (the external URL) from my notebook which is behind the firewall I'm able to login with my domain credentials as expected. If the other developer points to the same URL from their home which isn't on the domain they are also able to login using their domain credentials.

However if I am directly on buildserver and call SharePoint, TFS or Reporting Server from (i.e. http:// buildserver.mydomain.com:4800) itself using the external URL, I am prompted for a username and password. Entering my domain credentials results in another prompt to enter my credentials again. It will prompt three times regardless of which credentials are used (I have rights as a domain admin) and then after the third prompt directs me to a blank white page as though access was denied. There are no errors displayed on the page and nothing ends up in the event viewer.

From buildserver if i use just the host name (the internal URL), then I'm prompted a single time for credentials and it works. i.e. http:// buildserver:4800/tfs works from the server itself.

The behavior is identical for any service requiring authentication. Meaning from the box itself Sharepoint Central Admin, SharePoint WebApp, TFS, TFS Web Access, Report Server and Report Manager all fail using the external URL but will succeed if called using the interal URL.

So the problem comes into play when configuring all of the services to work together. The only way to configure TFS is locally from the server which means I must point to the internal reporting server url (http:// buildserver:4800/reports and reportServer respectively instead of http:// buildserver.domainname.com:4800 like they need to be) since external URLs aren't working from itself. If I configure TFS to use the internal URL for Report Server then creating team projects or working in the SharePoint site for the team project fails for anyone not inside the domain since their machines have no idea who http:// buildserver:/reports even is or how to resolve them.

I have configured Sharepoint with Alternate Access Mappings as well as set up Report Server to listen for external URLs. The external URLs simply aren't working when called from the server itself.

I hope this makes sense.
Thanks for taking the time to read this rather verbose plea for help.