the crow's nest

This is the reveal that the voice talking to him over the speaker does not in fact belong to another scared and lonely survivor at the bottom of the blood ocean (or at least, not anymore) but actually the beast in the depths. The same beast that he spotted in the distance and jokingly introduced himself to earlier in the movie, which has apparently been stalking him the entire time

That line puts this entire portion of the movie in a new perspective. But what I can't figure out is, what was with the questions about Filament Station shortly before it?

When Simon mentions the incident at Filament Station the Speaker becomes very upset and demands to know what happened there. Simon is initially confused about how the Speaker doesn't know about it and he doesn't want to talk about it, but the intense insistence from the Speaker forces him to explain

Before the reveal I thought that it must be because Filament Station held personal importance to the trapped woman Simon was speaking to and this scene was meant to show how long she had been disconnected from the outside world. But now, knowing that he was actually speaking to this cosmic monster...

Why didn't it know this? And why was it so insistent on finding out? Why did it sound angry even?

the REAL victim of the bite

He didn't do it.

The cops very clearly planted evidence on him because they had to make an arrest because all eyes were on them and whoever actually did the deed was making them look stupid.

Why would the real killer hero have kept the weapon on his person and traveled two states over while carrying it and a manifesto in his bag, conveniently turning the crime into a federal matter? The same guy whose bag they found in a park, filled with monopoly money? Why did the police turn off their bodycams, take Luigi's stuff, drive a block away, turn their bodycams back on, go back into the restaurant, and then arrest him?