Mine is similar... When cruising in 6th the display goes off. I kinda figured that it was normal. I thought that since you will be in 6th for a while it just disappears so it won't stay on continually.
As far as the wrong gear indicated...same thing with mine. Even when you "teach" it, it occasionally shows the wrong gear,no biggie.
I don't like the "hard" setting either..it seemed like when in 6th and the light went off, the throttle response was real funky. Some guys liked the setting though.
Your unit is doing what mine is doing so I'd say once you find a setting you like,,go with it.