Don't forget that the higher the speed differential, the shorter the reaction time. Even if you see it coming, in front or in the mirror, your ability to evade is reduced. This one isn't a v-squared problem, but once you've used up your reaction time, what's left over to actually move is a lot less.
Yes, but it is extremely unlikely there will be any problem in front of you since there are no side roads, driveways or drivers coming the other direction turning left in front of you. Also, from behind, everyone is going the same direction and has multiple lanes to do it in. The major danger on Interstates is at the entrance/exit ramps and cyclists have to be very aware at these points.
As noted, I would not ride any Interstate through or near a large city, even it it was permitted, as the interchanges are much too close together.