I don't know why the Foundation is containing this. There's nothing to suggest that they've bothered trying to figure out what the thing's anomalous properties are. It looks like they just decided to contain the whole building because weird stuff was happening with the residents. There is a relatively thorough description of what's in the building, but literally the only thing the article points out that is anomalous is the low red blood cell count, which they would have only found out about
Why are they letting a person of interest just live in the SCP? Why are they calling it a humanoid entity if there's literally nothing to suggest that he's not just a human that people mistakenly thought was dead? If they're interested in him, why can't they take him to a facility to run whatever tests they have and do an interview in a setting that they control?
Why is everything in the rooms still in place? Why hasn't the Foundation tried moving anything around, or taking some of it for testing? Why haven't they done tests with long-term inhabitation to see if the previous disappearances weren't just flukes?
You seem to have written a Foundation that either has completely inexplicable reverence for the thing they're containing or just doesn't give enough of a shit to try and make sense of what they're containing. Which, even if it's not as egregious as when the Foundation is stupid/jackasses/childish, is still nonsensical.
The article reads like you wanted the setup to be a specific way (rooms with specific arrangements of items, and the perpetrator continuing to live on in the building), and then didn't bother to justify either the necessity or the manner of the thing's containment. If you want to write about the anomalous world without fitting it properly into an SCP narrative, I suggest writing a tale. And this would make a cool tale.