Fridge Logic: Since his diving accident, Casey's natural state is being invisible. Okey-doke. Since he can only stay invisible for fifteen minutes a day or he'll disintegrate, they've given him a DNA stabilizer so he can stay visible. Fair enough. How did he stay alive long enough for them to get out of the sea and into a lab, diagnose the problem, and invent a solution?
And his invisibility is kinda haphazard too. Hospital gown and bandages? Visible. Normal clothes and DNA stabilizer? Invisible. Gun held in hand? Visible...
It might be that whatever he's touching at the time he turns invisible turns invisible, but things he comes into contact with later (like the bandages) don't...
And if tripolodine is such a powerful explosive, why not market it as, say, an explosive? Instead of using it as a prop in an ill-planned fuel-additive scam?
That one's easy; Dr. Hale is stupid. Why else come up with a ridiculously circuitous plan to... wait, what was his plan again?
Dr. Hale's plan was to say that he had invented a new fuel additive, embezzle the 10 million used to finance the project, and then fake his death. Everyone will assume that a big oil cartel killed him because he going to make them obsolete. Which is why he staged the thugs attacking him in the parking lot.
Not to mention, what was the point of Denby's evil plan to blow up a random jet some... where for some... reason? And then to blow up his own expensive race car? They didn't even bother to attempt to make-up a motive for this guy. The whole investigation into how he did it kind of glosses over why he did it.
He's a freelance industrial saboteur. He's getting paid by someone who for whatever reason wants the jet and the car blown up. Denby can do it because he came up with a way to send a signal to a chemical and cause it to explode remotely with no trace. Either that, or the jet and race car were just testing to see whether he could do it or not. Being able to blow up something remotely is incredibly usable.