Question: Why did John's house suddenly alter so drastically when Jack's hand was blown off in the past? Did this one event somehow turn John into a better interior decorator?
Answer: The house changed because John's life changed, with both his parents alive to nurture and guide him, he became a different person. Different lifestyle and attitudes.
Question: What is the point of Dennis Quaid throwing his helmet out the window when the factory is on fire in the beginning of the film?
Answer: Firemen never get rid of their gear in a fire, especially not a helmet. He was unable to reach via radio his crew and when he threw his helmet out the window, it told his crew that he was in trouble and what his position is. They also then have a clue that he is still alive.
Question: How did John's father appear at the end of the movie as an old guy? It's very confusing to me, can someone please explain how that worked?
Chosen answer: His son prevented his death in the past. By warning him about how he originally died in that fire and changing his decision, and then convincing him to stop smoking so he doesn't die of lung cancer. He prevented his past death, so suddenly he was still alive in present time.
Question: What did John mean when he told Jack at the bar that Jack's mother was the nightingale and it would have led to Jack? Did Jack kill his own mother? Also why did Jack Shepard, a supposed serial killer, stop killing?
Answer: Florence Nightingale is considered the founder of modern nursing and nurses are often called "nightingales." It has nothing to do with Jack's mother telling on him or "singing like a bird." Whether or not Jack killed his mother is left ambiguous, but it does seem like that's what they are suggesting. In the film we are told Mary Finelli was his first victim. However, they seem to imply that Jack's mother's killing was not associated with the "Nightingale Murders." Had the police connected her murder to the "Nightingale Murders", it night had led them to Jack. So Jack changed his M.O. after killing his mom, which I take as targeting younger nurses. In the film, Jack's dad tells John that Jack got caught up in the Knapp Commission, which was an investigation into police corruption. Jack went to prison, which is why he stopped killing. In the film, it's suggested that perhaps the killer (before they knew it was Jack) was taken off the streets (i.e. sent to prison for a crime not related to the killings) and smartened up once he got out of prison. There's no suggestion that age or lack of testosterone is what stopped Jack from killing after getting out of prison. Of course, it's also possible he did kill again, but due to the gap in killings, those murders aren't related to the "Nightingale Murders." But all that is speculation since they don't really reveal any of that information and it's not central to the plot.
Answer: I can answer part of your question. Most serial killers are under the age of 50. Testosterone levels drop after that age, and it is thought that this may reduce a psychopath's urge to kill. The nightingale reference may be the same as the slang term, "to sing like a bird," which means someone gives up information easily. Jack's mother may have provided info about her son, either knowingly or unknowingly.
Answer: Or maybe Jack's mother abused him as a child, and that's why he hated her and killed her, and then became a psycho serial killer. He continued to kill other nurses because his mother was a nurse.
Question: Instead of Frank giving the wallet with the fingerprints to John in the future, why didn't Frank just give the wallet to the police in his own time?
Chosen answer: They couldn't be sure that the police wouldn't lose it or turn it in when the owner showed up. Or, since we find out that the killer is a cop, he could have just taken it back from evidence.
Answer: Too much explaining would have to be done by Frank. The police would ask why he would want his wallet scanned for prints. Plus remember they were on a time frame. Julia was going to be killed in a week, and they were trying to save the other girls as well. Quicker just to get the wallet to john, and he would go scan for fingerprints right away.
Answer: Plus, they didn't have some of the technology in Frank's time as they had in John's.
Question: Was Jack talking to himself in the past as well? When Jack attacks John he says "Watch me steal your life away" and then young Jack attacks Frank. Young Jack also knows John by name as he says hello to him when he walks in to find his mom being attacked.
Answer: During that scene the radio was like an" open 2 way line" that everyone could hear. Frank heard John and future Jack fighting. John heard his dad fighting Jack. Jack heard Frank yelling John's name. The shot gun blast was echoed in both times. It is filmed in a way that the sounds from each time could be heard.
Question: After Frank survives the Buxton fire, John rings his mom and goes through to her voicemail. The next day he tries again and gets through to a Deli (obviously because his mom has been killed and therefore someone else has what would've been her phone number). How did this work exactly? His mom died a long time ago from his perspective, one day isn't going to make a difference since it happened in the past. Can anyone explain this or is it a plot hole?
Answer: There are 30 years separating Frank and John, but it seems that the timelines are parallel and unfolding at the same time. Example: if something happens on October 10th 1969 at noon for Frank, any repercussions from that will unfold for John at October 10th 1999 at noon. We see evidence of this when Frank burns the desk, when he survives the fire, when he shoots Jack's hand off, etc. After Frank survives the fire, he comes home and has a conversation with John. After they talk, John calls his mother (Julia) and gets her answering machine. Then, keeping in mind this is happening in a parallel sense, young Julia in 1969 saves the life of her killer, setting in motion a new future in which she is killed. It is then when a sleeping John in 1999 starts getting memories of his mother's funeral. So, when he called and got her machine earlier, she had not yet saved her killer's life in her timeline. After she does save his life, John wakes up and tries to call her, but gets the deli instead.
Answer: John calls his mom, which goes to voicemail, before he uses the ham radio where he ends up talking to his dad. At that point, the timeline hadn't changed, his mom was still alive and his dad still died when he was a kid. The timeline changes (along with getting new memories) after his dad decided to listen to John's advice and make different choices.
Answer: Because the house is no longer John's. In this universe, his parents still live there.
Brian Katcher
Or he lives there and his wife redecorated.
I always took the scene at the end with Julia and Frank getting in a packed car with an older looking Elvis as them moving and leaving the house for John. And as I said above John's wife must have moved in and decorated.