Any experience??

[tursiops]

I an provide details of several oxygen toxicity fatalities, but all of the are on technical divers. I do not know of a case of anyone known to be have gotten oxygen toxicity on NDL dives. By the phrase "known to have gotten oxygen toxicity," I mean that a surprising percentage of diving fatalities include people who died alone with no clear cause of death. According to an old DAN article, that includes the cases of people who might have had oxygen toxicity on dives while using Sudafed but with no clear indication of a cause of death.

Let me try and rephrase the OPs question in post #1: "Is O2 toxicity a real thing or were they just trying to scare me in my AN class?"
Ans: It is a real thing. You can easily avoid it by following the guidelines; otherwise, you are playing Russian Roulette.