Audio problem: In the scene when he goes back to his home and finds his dad on the floor, he walks into the house and you can see Family Guy playing on the tv and hear it very quietly. Unfortuanately, the audio is coming from a completely different scene in the episode than the video. (You can see Lois is in the zoo, which comes from the beginning of the episode, yet the conversation you can hear is when they are sat in the kitchen towards the end of the episode.)
Audio problem: When David teleports to the clock face of Big Ben in London, the clock strikes the hour. Yet the clock hands show half past the hour.
Answer: In the novel that this movie was based on, his mother was killed and David does go looking for the man who did it. Those doing the summaries are just confusing the two different versions.