It sounds ot me like you are doing lots of things right with the praising and going on command. It seemed to take my minpins forever to realize that their business belonged outside and outside only too. It all sounds very familiar. Do you have Brad's E-book? One thing that helped me get the idea through my dogs heads was the reprimanding when they didn't go outside....whether it was a minute, an hour, a day or a week later. As soon as I started his technique for this, things improved! And even now if I find something, like my shoe, in an odd place I can just say "Who Did It?" and both dogs go into a submissive posture and look at the object and then go off when given the release command and lie on their beds with their heads down.
Just a note...beware of "talking" to them at close range after eating tuna...they are more concerned with your breath....

Hope this helps some.