Since the villain's plan called for finding a patsy to pin the blame on, logically they should have "promoted" the employee who scored the *lowest* on the test instead of the highest. They wanted the dumbest, most gullible person possible since he presumably would have been the least likely to figure out exactly what was going on. While looking at the test scores, Cliff expresses his knowledge of Fred being a "dunce and witless" and may very likely know that his test had to have been switch which someone else. They also should have terminated the person with the *highest* score, for the opposite reason, which they did after checking the scores and assumed that Barney had to be the one that Fred had switched tests with.
Fred asks Betty if she wants to dance right after the BC-52s finish their set and say "Good night". However, Cavern on the Green could have another band appearing after the BC-52's, just as its real life counter part (Tavern on the Green) was once frequented by musicians.