For those trying to get the Harmony up to speed...
To emulate the Back button on the Fire TV remote assign the clear key from the ORtek.
To emulate the Home Button on the Fire TV remote assign the Browser command from the ORtek. It is also the upper left key on the remote. The "e" with a circle around it.
On my Harmony One I assigned Home to the Menu key and Back to the Exit key. Neither were being used for the ORtek device.