Yeah. Like the first thoughts you start with Hot! It's hot! All over my body it hurts! since the tittle says Jon's POV I would beleive those are his 1st POV thoughts but seconds after you wrote "Engulfed in darkness, Jon could barely make out the inaudible screams of people around him." This phrase made me wonder if the Hot! were the screams. Since it combined 1st POV thoughts followed by a 3rd POV description it can somewhat get confusing.
After that many of Jon's thoughts are shown to us in 1st POV with the exception of "Is this really the afterlife...? Jon taken aback, thought to himself as he surveyed the room."
That phrase fits perfectly with the rest of the 3rd POV view descriptions.
Again there is no rule against combining 1st POV thoughts with 3rd POV descriptions it just throws me off guard to be put in the characters shoes just to be taken out of them seconds later to get put back into his thoughts and then thrown out of the character again into a narrators POV.
For me it feels like you tried to use Jon's POV as an excuse to avoid writing Jon pondered to himself in 20 different ways. Thus why you combined 1st POV thoughts in a 3rd POV story.
P.S. I am mainly a 1st POV author (that is why I am more suceptible to this changes) and this is just what I feel in no way am I trying to insult your work. This is a personal opinion and you should remember that rules in writing can be broken depending on the style of each author. I beleive it was Stephen King who once said that you must learn the rules in order to know how to break them.
P.S.S. Hopefully, what I mentioned can help you grow further as an author as I truly beleive that the 1st POV thoughts of Jon combined with the rest of the story in 3rd POV can get confusing. Not allowing the reader to know if they should be in Jon's shoes or stay on the narrator's shoes.