Other mistake: When the hitman returns to kill Bernie for the last time, he shoots Bernie six times and the revolver is empty as expected. When he pulls out his other .38 revolver to shoot the witnesses, he shoots seven times even though .38 revolvers can only have six bullets. (01:29:00 - 01:32:00)
Other mistake: In the opening scene in the office, when Andrew McCarthy says, "Let's go to the beach" and runs off, you can see that the other guy's PC, which he has been working on, has no power cable plugged in.
Answer: He says the Italian word "cornuto." Basically insulting Bernie for sleeping with Vito's girlfriend, which is why the hit was put on him in the first place.
Bishop73