By god, it is good to have you back. Strong vocabulary, logical statements, and actual proof. These are the things that have been lacking for quite some time now on the base, well somewhat.
As for the original post, I say to you: It is quite possible that Kakashi could sever said lightning bolt, and foresee its coming. Although I can't get over the distance factor. Let us assume that most battles between shinobi of this level, S Jounin and upwards, are fought from anywhere between inches apart from each other and let's say thirty yards or so. Sound reasonable? I'll assume yes. As you've stated lightning travels at varrying speeds, depending on air conditions and all, but I'll take your word for it at 3,700 miles per second. That is astonishingly quick, and I doubt Kakashi in any way can move that quickly. So even if he were to e inches away from it and even with precognitive vision, I doubt he could do it. I say unless the lightning is on a direct course towards him, he shan't hit sever the aforementioned lightning.
I so however give you mass amounts of praise for this thread, and do look foreword to hearing more from you.