When Ellie is beginning to open the trap door in the floor her flashlight is on her shoulder. As she tries to look in to the area below the trap door she takes her flashlight out of her bag.
On Frank's last day the boat that Bill used as a hauling trailer looked old and worn. When Joel and Ellie arrive and Joel goes to the garage to find the truck, the boat is seen in pristine condition in the background.
Bill continues using a gas generator and has a gas-powered car ready to go twenty years after the start of the infection, when there is no way gasoline would last that long. Being a survivalist and chemist, based on the various chemicals Joel finds in the garage, Bill would know this and have planned for it. It's also likely that part of Bill and Frank's deal with Joel and Tess included deliveries of whatever FEDRA was using to power their vehicles.
When Ellie goes into the basement of the store, everything has aged as it has deteriorated, such as the lockers. BUT the galvanized trash can is rust free. If exposed to the same environment as everything else down there, it should have been at least fairly rusted. Instead, it looks like it was just brought home from the local Ace Hardware.
When the scavengers attack, multiple people catch on fire, but the flame throwers appear to be stationary. For multiple people to get hit by them would require the people to willingly walk into the path of the flames.
Bill starts off using a boat as a makeshift trailer, but continues to use it over the years. It makes sense that he used it at first, but there was no need to keep using it after going to his local Home Depot. Home improvement stores like that sell trailers designed for hauling cargo, and would haul a lot more stuff than a boat, and would be a lot easier to load and unload.
Teenagers are capable of handling small firearms. So, given the apocalyptic situation, Joe would have allowed Ellie to taken an appropriately-sized rifle and pistol when they left Bill and Frank's house. Ellie wouldn't have had to sneak a pistol in her backpack.
At the beginning of the episode, Joel and Ellie are camped in a mountainous wooded landscape that's presented as "10 miles west of Boston," but appears strikingly unlike the dense, predominantly hardwood forests in eastern Massachusetts. Much of the show's filming took place in Alberta, Canada, which lacks natural landscapes that closely resemble the U.S. northeast.
Bill's neighborhood could conceivably get its power from Bedford, MA, which is adjacent to Lincoln, MA, but not New Bedford, MA which is roughly 70mi further away.
Considering the dangers they will be facing from infected and humans traveling across the country, it was unwise of Joel to not take advantage of the large store of guns and ammunition in Bill's armory to teach Ellie how to properly use a firearm. It would have been much safer for the both of them for Ellie to at least know how to properly and safely use a firearm, even if he didn't feel she was ready to carry one. A gun in the hands of an untrained amateur is dangerous, which is what winds up happening when she finds Frank's gun and hides it. But with proper instruction Ellie is more than old enough to responsibly handle a gun, kids in real life are taught at much younger ages than her.
Joel says that it's believed that the infection happened all at once due to infected food stuffs. However, there is no food which is eaten globally and no way that food would be distributed evenly around the globe so that everyone would eat it over the same couple of days. In reality, outbreaks would have been occurring sporadically in different places over time, allowing authorities a much better opportunity to contain it.