Did Chuck *want* Ernesto to hear the tape?
Seems like Chuck is setting up a long play. And the talk about "vérité" with Howard at the beginning might also have been forshadowing of Chuck pulling a fast one on Ernesto.
I figure Chuck wants Ernesto to tell Jimmy about the tape, and this way Jimmy will feel threatened, but Chuck will have "clean hands" because he hasn't actually revealed the existence of the tape to Jimmy himself. He even covered his ass further by emphasizing to Ernesto that Ernesto is legally bound not to reveal the tape's existence, even though he secretly expects (and hopes) Ernesto will tell Jimmy. This allows Chuck to cause the threat of the tape's existence to reach Jimmy's ears without being accused of blackmail.
In a similar vein, he may be hoping that Howard will reveal the tape's existence to Kim.
Again, this is a way for Chuck to screw with Jimmy but maintain a facade of propriety.