How, exactly, does that double-barreled pistol reload?
Most likely from twin clips, and it's never shown re-cocking while the barrels are deployed, which would make sense.
Car cut in half, but still drivable because it's front wheel drive? Plausible, but isn't the gas tank usually toward the back? (Given how modified that car is, it's reasonable that the gas tank might have been moved)
A number of the FX in this movie (the method by which the Hornet and Kato escape Chudnofsky's death trap, the elevator cutting the Black Beauty in half, and driving the Black Beauty after it was cut in half) were tested by Adam Savage, Jamie Hyneman, and the rest of the crew on a MythbustersGreen Hornet special (featuring a guest appearance by Seth Rogen). As you might figure out on your own, only one of the effects (driving the Black Beauty after it is cut in half) rated as high as "plausible", and that assumed extensive modifications to the car.
There was a flamethrower in the front, so maybe they put a fuel tank in the front for it?
That's exactly what happened: at the scene at the gas station, you see Kato pop out the hornet symbol from the front grill to fill up.
When Britt was a child his father told him there was no point in trying if you fail, resulting in Britt never attempting to make anything of himself. Kato, in contrast, has tried multiple careers (as shown in the comic book prequel) which have all, humorously, failed, and by the time of the movie has resigned himself to being a newspaper mogul's engineer and coffee boy.
Britt's father angry at him for taking some chick into his garage hints at the fact that they've all been tricked out with armor plating and gimmicks because the guy was cautious of running afoul of both the crime lords and the DA, and letting any stranger in could compromise the secret.
Britt mentions that his father's statue looking over everyone only reinforced his Jerk Ass image, citing that as the reason to decapitate it. At the end of the movie, the statue is fixed, only the head is now crooked downward, because for the first time in his life, Britt can look his father in the eye.
The more lighthearted tone of the film itself...the serials, tv programs, and comics play the story out very straight (compare and contrast the Adam WestBatman to The Green Hornet featuring Bruce Lee).
Britt being an inexperienced fighter who relies on Kato when facing multiple opponents. In the TV series this is why Britt had Kato in the first place, to watch his back.
Britt Reid decides he's going to fix computers for a living before his dad gets done in. What's the one thing the Hornet has that we don't see Kato make? The website!
The film is a treatise on identity and perception. Britt's father is seen as a great man, but Britt and Kato know how he is in private. The duo pretend to be villains to be perceived as having no ties. Britt plays up his buffoonery to avoid suspicion. And Chudnofsky's entire arc is one Villainous Breakdown focused on the fact that he isn't seen as scary. Many films focus on personal struggles for heroes, but every part of this film, more than any other superhero movie, work with how people are perceived and their identities in contrast with how they are seen.
When Kato tells Britt he's from Shanghai, to which Britt responds "I love Japan." On the surface it sounds like he's an idiot that can't tell the difference between China and Japan. But on the meta level it plays on the fact that the Kato before Chou, played by Bruce Lee, is a Japanese man played by a Chinese actor.