I've never witnessed any spooking of the fish from the sound. Considering I have discus, which are probably one of the fish that spook the easiest, I am happy with the location of the tank and the TV. In fact, I could almost guarantee where my Loricaria So.Rio Atabapo are right now, in the corner closest to the TV as that's where the food goes in. They never leave.
With regards to your second point, this isn't an issue as I mentioned previously due to the good quality lid. I don't get any noticeable evaporation so it would be fairly safe to assume that there would be a very limited increase in humidity in the room.