Agreed. The LRC podcast interview with Kerr gets his take on a lot of these and other variables. He said the extra 1% to chip away at the WR are technology, spikes, tracks, pacing, understanding from his coach on how to best prepare him, his nutrition, and his mental training.
Looking back at the 2024 Olympics specifically and factors that might help him run faster than he did then, he mentioned running three rounds in five days in Paris and the bad sleeping conditions for athletes in the Olympic Village, saying, "You saw those cardboard beds. You saw what we're dealing with from day to day."
While all those factors add up, I think your letter e above is the biggest one. Making the WR an outdoor season priority and attacking it while in peak shape is what will give him his best chance. It's a small chance, but I agree it's not 0.
Even if he fails miserably, I give him credit for going for it and calling his shot so far in advance. He could have easily reflected on his career and accepted that he's a championship racer rather than a time trial runner, and there would be nothing wrong with that. Instead, he's pushing himself to try to take down a longstanding record. I respect that.