IIS ARR interferes with TSG?

RDP works fine with IIS set to auth (direct to https://my-domain/ requires login auth), but it seems when I try to set up a Reverse Proxy using IIS, URL Rewrite and ARR ( having https://my-domain/ show http://internal:88/ ) the website works fine but TSG stops working.

Machine -> ARR -> Enable Proxy /* ARR feature only avail at machine level, not site */
Machine -> Sites -> Default Web Site -> URL Rewrite -> "(.*)" to "http://internal:88/{R:1}"

My Goal is to have only 443 forwarded from WAN to TSG w/IIS and:

1. TSG avail for remote admin of internal machine[s]
   
2. 443 show an internal server's website (not TSG's) with auth enabled so login is required to view.

I have gotten one or other to work, but not both.

https://blogs.iis.net/carlosag/archive/2010/04/01/setting-up-a-reverse-proxy-using-iis-url-rewrite-and-arr.aspx