Sorry, but I have no near term plans to implement something where a different domain/hostname is used for authentication, there is no real need for it that I know of if you just use an ssl on the main domain/hostname.
I don't know about the redirect loop, you need to be careful with IIS url re-writer rules to make sure they do what you want and only what you want. I don't know anything about the url re-write rules you have configured and cannot offer support for IIS Url re-writer, you will have to find help on the web for that.
Best,
Joe