Since Hal wants to maintain the majority of the reactions to after the message cuts off, I think the solution would be to include the scene from later where they decode the message but instead of the sith language being played you have “the work of generations is complete” cutting “the great error is corrected” and going straight to "the day of victory is at hand, the day of the sith.

I think the most important thing, in this case, is to convey the most with the least amount of words possible.