Trying to help you without forcing a complete rewrite, since you are two days out. Also, trying to stay within the bounds of the story you've written.
My main criticism is that I don't know anything about these characters along the way or by the end. No matter the story, people want to see/feel/hear something in the characters in a story that they can relate to. That's what makes them go along for the ride.
You have an opportunity in the van for Vince to say something about himself somewhere before or in between or after the radio broadcast without doing major rewriting. Maybe he's talking to the body. Daniel is a little more problematic, but I think you need to at least give us a clue as to why he wants to be killed.
I think the boner business is a little unusual, but certainly evidence of how erotic this is for them. It might be funnier though if the boner is followed by a sound or facial expression that adds to the idea of how sexually arousing killing is for Vince, then bookend it with Daniel doing the same sound or facial expression to emphasize how they've switched places. Be creative here. Maybe you've got some clever/funny way you're going to shoot these guys' hard-ons?