Why is the pharmacist armed? Because he's trying to maintain order to get people the medicine they need, and he expects to encounter drug addicts after the prescription-strength painkillers.
There are real-life pharmacies in the US with guns, in case of attempted robbery. As mentioned, they are tempting targets for those addicted to prescription drugs or methamphetamines (which are made using cough medicine).
Did you ever think why the helicopter refused to arrive before dawn? Simple. The flares would be a dead center target for the zombies since they're sooo shiny.
I'm pretty sure that the helicopter just had other things to do during the night. It was a chaotic situation, after all.
Plus during the day, you can more clearly see who is infected and who isn't, which would be critical in an evac situation.
One moment in the book becomes this with the benefit of hindsight. The Battle of Yonkers ends with a squad of Joint Strike Fighters bombing the zombies in a last-ditch effort to slow down the horde. In the book, the Great Panic started in the summer of 2013; as of 2014, the Joint Strike Fighter still has not entered service. Instead, it has been the subject of endless delays and cost overruns, all for a plane that was found to have inferior performance to comparable Russian fighters. It is viewed as a symbol of everything wrong with the military-industrial complex... in other words, kind of like the Battle of Yonkers in-universe.
Furthermore, the appearance of JSFs at Yonkers, despite them not being in service by 2013, could be given an equally appropriate justification — the Pentagon could easily have hurried a few prototypes into service in order to have another piece of state-of-the-art military technology to show off to the press, despite it (like so much of the gear at Yonkers) being largely unsuited to fighting zombies.
From the book: Why are there so many "La MO Es" (Last Men On Earth, the name the reclamation forces gave to people who survived the outbreak but didn't want to re-integrate back into society) alive even after America started retaking the country? It's because they are the crackpots who read the Zombie Survival Guide and prepared for a Class 4 Outbreak. An earlier interview had even an American dismiss the book as "masturbation material", so of course only people who want to opt out of civilized reality would be the ones crazy enough to prepare something like it.
Why did Israel fall? Because they decided to fortify Jerusalem! In the book, Jerusalem was described as a weak point if it was made part of the wall.
How does Tommy escape his zombiefied family? Given events later in the film, it's likely that the boy is terminal.
Unlikely, as you see him being chased by his zombie father. He wouldn't have been chased if wasn't healthy. Tommy probably escape during the twelve second window of the transformation, and probably only got to Gerry by Plot Armor
Considering that it appears mostly deserted, is everyone in Wales dead, evacuated or just keeping really quiet?
Notice how every zombie is just a a man between 20-40 or so...you never see any babies or old men..which make sense as the virus is trying to spread itself as efficiently as possible and most babies can barely even walk, much less chase after healthy humans..but that means that many babies are starving to death...
In the movie, Tommy escapes the zombie attack, as well as the zombification of his family. He shoots a zombie that is trying to attack Gerry. When Gerry, his family, and Tommy reach the roof of the apartment building, Tommy's zombified father attacks. Given the presence of Tommy's gun and the absence of his mother, it's very possible that he had to shoot his zombified mother to escape.