I have the same fridge and I've just sent him an email as well..
I used to run mine on setting 6, but now run it on 4..
I don't use a thermometer any more as like you , it was all over the place..
The beers are always nice and cold ( but not icy cold as I like them ), so I figure every thing else is OK as well !!
In hot weather it will run for a LOT of the time, but still seems to keep the things cold.
In cold weather it cycles very good, but I've noticed the freezer has let a few things thaw out
If I had the room and my time again, it would have been ditched in favour of a chest style fridge..