Your answer makes sense. Regarding [1] I do believe that your right, without air resistance the escape velocity is the same regardless of direction. The reason I chose the speed of ISS is because the escape velocity to enter into orbit it he speed needed to maintain that orbit. So in order to reach an orbit that parallels the ISS you would have to get up to the speed of the ISS and not necessarily any faster.
No, direction does matter. Perhaps we're confusing things by talking about escape velocity instead of orbital velocity. We want to reach a certain orbital velocity with respect to the Earth as a reference.
Think of it this way: if you were approaching Earth from space and wanted to enter orbit with the ISS, you need to reach a speed, e.g. 17,600. The speed is the same no matter where you are coming from, such as from the Earth's surface.
On the equator, if you take off east, you already have about 1,000 mph working with you. If you take off west, you need to get an extra 1,000 mph. Towards the poles, the (dis)advantage lessens.
I agree on the East vs West if we are aiming for orbital. I disagree on the speed being the same even at the surface, as (I think) you have to subtract the gravitational deceleration as you get from the surface up to the height of orbit. Coming from space you gain speed coming in, so this is not an issue.
Details aside, the overall conclusion remains that rail guns are not likely to be a useful means of propelling squishy cargo like humans into space.
