Yes, so it’s dead.
I’m not entirely sure what actually happened, here’s a picture of the RPi though:
I had a realization of what might’ve been the cause for it dying when I woke up earlier. I noticed that there was a lot of water condensing on my window, so I suspect that since the charging port is negatively charged, the neutrally charged water vapor particles were attracted to the charging port (which also explains all the dust around the port), thus a redox reaction occurred, essentially rusting the charging port, which also explains the brown matter on the top of the port.
This does not explain the melted plastic around the base of the RPi though, I can only assume that the port must’ve shorted out and heated up - melting the surrounding plastic in the process.
Either way, now I know not to put such devices near places where high humidity is present.
In the event of this, for christmas I’ve got myself a Mini-ITX Thermaltake F1 and another RPi 3B, so hopefully things go better this time around.