I don't flat much (well, at all, knock on wood), so I could be terribly wrong, but my understanding is that underinflation can lead to "pinch flats." A 3-inch gash in both your tire and tube suggests to me that you ran over something nasty.

For what it's worth, I run my Rubino Pros around 100 psi. According to the chart, I should run them at 92 psi.