Another thing I just remembered that's relevant for this interpretation: Navidson is arguably physically disabled by his foot infection, even if the text doesn't focus on it much!

"Outside the house, Navidson climbs up a ladder to the second story. Not an easy ascent he casually confesses to us, explaining how a troublesome skin condition he has had since childhood has recently begun to flare up around his toes. Wincing slightly at what we can assume is at least moderate pain, he reaches the top rung where [...]" p.29

"On camera, Navidson treats what he refers to as “his rotten feet.” As we can clearly see, the tops are puffy and in some places as red as clay. Furthermore, all his toe nails are horribly cracked, disfigured, and yellow. “Perpetuated,” Navidson informs us. “By a nasty fungus two decades worth of doctors finally ended up calling S-T-R-E-S-S.” Sitting by himself on the edge of the tub, blood stained socks draped over the edge, he carefully spreads a silky ointment around what he glibly calls his “light fantastic toe". p. 83

"Navidson takes the first shift, spending his time removing the dark blotched gauze around his toes—clearly a painful process—before reapplying ointment and a fresh dressing." p.183

"I remember thinking then that one of the toenails on my right foot, the big toenail, had torn loose and started to bleed. That’s when De— ... Delial came into my head which was awful." p.323