Movies work if and when the characters in them work - we understand and sympathise with their reasons and motivations and these tie directly to the plot of the movie. This is the biggest reason why the OT is better than the PT. If the audience loses touch with the emotions of the character(s), the movie ceases to move them. Now, as soon as Ben tells Luke his father is out there, Luke will have a specific goal - to find and confront his father- which is quite separate from his goal of rescuing the princess (and by extension the galaxy). However, for the rest of the movie, he makes no effort towards this goal. His reaction when he sees his father ("Ben!") is totally inappropriate. Thes factors will put the audience in a position of not understanding their hero - fatal for any movie.
Also, Luke's reactions toward Vader in ESB are totally inappropriate to the scenario you describe.
If you are set on this basic idea, I think you'd be better advised to just cut the "betrayed and murdered your father" bit from Ben's hut and figure out a way to have Ben tell Luke the truth about Vader on Dagobah in ESB.