For the guy who ended up in a bad place, I strongly suspect that given that smell is often considered the strongest/deepest sense, and he'd just had a ton of pus come out of his stomach, and had the tubes that normally contain faeces, along now with pus, ripped open, that stench would have had a strong effect on what his addled mind was experiencing. I don't think it's chance that he's repeatedly talking about the smell (and he'd no doubt have been feverish too with a lot of rot going on inside his body).
That would seem plausible, yes. Those who've experienced NDEs can see and hear everything that's going on, so being able to smell things could be possible too.