The cold and wind were absolutely the determining factor in making it so difficult. It would have been a challenge regardless, but the cold made it virtually unbearable, at least for me.
At mile ten, there was a backup at the "ring's across water" (Hang Tough) and a wait of about 20 minutes in the cold wind. The standing around and waiting while freezing zapped whatever energy I did have, and I never recovered after that. It made the rest of the course (two miles) miserable.
I wouldn't have done any additional running to prepare, I felt very good with my running and overall performance. If you can comfortably run 5K, you'll be fine.
February means 'bulk season', so I'm probably carrying 10-12 pounds more than I would be in the summer months. Being a bit leaner would have definitely made the bars and rings easier, but with fingers you couldn't feel, and muscles that felt frozen up, I don't know that it would have made much of a difference.
I think the people who would do the best are the lean, 160 pound agile 'body weight exercise for hours' pseudo-gymnast types, of which I am not, nor do I desire to be. But in the end, it really is about mental determination more than physical strength and endurance.