At Dylan's funeral, after his mother discusses his smile with the funeral director, you can repeatedly see the corners of his mouth twitch as if he is trying not to laugh.
Early in the movie when Dylan and his mother are pulled over by a State Trooper, the officer says that they're cheering for him at the "14th Precinct." Pennsylvania State Police don't have precincts; they have "troops" that use a letter designation system. If anything, the officer would've said the entire "barracks" was cheering for Dylan.
When Dylan sees the jumper, the camera pans down from the top of the building, showing that the lady jumped at least 15 stories; yet the roof of the SUV she lands on isn't indented at all.
The film makers left the viewer to interpret if Dylan and Nikki had sex that last evening. There is evidence to support both possibilities. Evidence that they had sex includes the smile on his face and the emotion of Nikki seeing him dead. The evidence to support there was no sex is that the request was for a "weekend alone" (not sex) and they were still dressed.