No reasonable person would have been confused into thinking it was an official IKEA game; IANAL, but it seems unlikely to me that IKEA would have ultimately prevailed in court, though a simple change to the color of the logo would probably have been helpful to the devs of the game.
It's a direct ripoff of https://scp-wiki.wikidot.com/scp-3008, a popular sci-fi horror story set in an IKEA. At the time the game was also using IKEA's brand colors.
Yeah, that seems like the type of thing that should at least in theory be fair use.
IANAL either, but could this be a trademark issue? My understanding is that if you don’t defend your trademarks you risk legally losing them.