The second part, about impact, I'm a bit hesitant about. It probably wasn't your intention to say that (to paraphrase according to my understanding), 'going into a pothole at a faster speed will turn out better for you than going into it slower,' because this is often not the case since FΔt=mΔv. However, it is true, as you said, that braking is NOT a good response when you notice the pothole in front of you too late and will result in all sorts of damage to your tube, wheel, self-esteem, and even fork. As you explained, this increases the 'm' in the above equation, causing a larger force on the wheel.
So, don't brake into potholes. Instead, avoid them by any means possible. Until that becomes automatic, don't use skinny tires.
As a side-note, I've been riding with 23s for about 6 months now without any problems with the above advice. Our roads are so bad we got state grant money to fix a section of my daily commute.