I think the guy at the counter is a former Cafe Poirot employee. A customer wouldn't know about a rack under the counter, or where something like herb salt would normally be stored. Alternatively, he may have been the one to move the herb salt there in the first place, to create a pretense to make Azusa leave to buy it and thus be susceptible to kidnapping.
The serial killer is obviously a red herring. Personally, I suspect the head in the fridge is fake. An actual severed head just feels pretty heavy for Detective Conan. Leaving prisoners/hostages so close to a bloody knife and saw is also a bad idea for kidnappers, they can fight back with that, so I think those could be fake too. Meanwhile, the fact they're wearing the masks and glasses shows they don't want to be recognized, so they probably don't intend to kill Conan and Azusa. (Also, I'm amused that the guard has their phones in his pocket. Could've just left it in another room...)
Anyways, the two main suspects: Counter Guy and Game Dude, with the motives being the tug-of-war contest and the game.
The tug-of-war contest might have a deadline for teams to register at midnight, so kidnapping them would guarantee Ran couldn't sign up since she'd have other priorities. If the guy at the counter was a regular or employee, he'd know Ran is super strong, and want to keep her out. Would also explain why Conan was kidnapped along with Azusa, would guarantee Ran would be directly involved in the search even if they called the police. Though... that's pretty extreme for a contest that's A) all women, so the men involved aren't participating; and B) the prize is a total of six 10,000 yen.
For the game though: I'm 99% sure that reflection is for Splatttter III. Look at the roman numerals next to his head's outline, the visible bit of the cut-off character matches with the other ones. So they could be announcing it at midnight, and want to make sure she doesn't tell anyone beforehand. If this is a ploy by the game's developers though, kidnapping someone, traumatizing them and breaking their belongings (the detective badge) would be really bad for PR if they're discovered...