Good point about the first extra point early in the game. Silver would say the difference between 10-7 and 9-7 is greater than 9-7 vs. 8-7. But once again, fail and the coach is more likely to get second-guessed by those with conventional wisdom if they fail to convert.Lost in all of this is Iowa's decision to kick the extra point after taking an 8-7 lead after the safety and ensuing TD, which I questioned at the time. The extra point made it 9-7, but Nate Silver's chart shows that going for two would have been the much better statistical alternative. Had Iowa converted and taken a 10-7 lead, no subsequent two-point conversion would have been necessary. And, a failure to convert would have made clear that a pair of two-point conversions were necessary as the game neared the end.
One thing the chart doesn't capture, and what I think some on here are trying to express, is the emotion/momentum that exists after having scored. I'm guessing Silver's chart is correct in a vacuum, but sports aren't played in a vacuum. We've all seen instances of teams losing leads because they start to play tight, or not to lose (e.g., Nebraska). I thought going for two was the correct choice because I'm more in the Nate Silver camp, but I can see why the counter arguments are being made.
About your second point.. As a 2-point conversion attempt always follows a touchdown, doesn't the offensive team always have the momentum?