Eroos
Really a frikking Panic attack? Also why is afraid of dieing that much, isn't he died once? Death Anxiety stems from knowledge that his life will end and the fear of unknown. Also his is moral compass should become loose. If someone already die their fear and anxiety should not appear. Even if someone have experience near death experience irl people will become more of a risk taker and adventurous & enjoy his life with less fear.
In the face of imminent death it is difficult to have a rational mind. Keep in mind that the protagonist practically lived a whole boring life, without even having the slightest emotion or doing something as normal as watching a movie. For him it's the first time he's done anything besides working or studying, so his weak heart couldn't quite take it in its stride.