exactly, their explanation of the backwards-in-time-travelling bullets started making less and less sense as the movie went on

Given that a defining characteristic of time is that the universe will move from an information-filled organized state towards increasing chaos as entropy increases, maybe the whole movie is moving backwards through time?

My wife is a pretty even keeled person. Tenet made her visibly angry and to this day, I have to consider her current mood before I mention it.