First of all i don't see how you "should be not there" when there's an atack. Some people here dream of using Kotegaeshi in a real fight just like in the Dojo, well i don't. O'Sensei said "70% of a fight is atemi". I believe we use atemi to "distract" the oponent, and THEN make a throw or arm lock. If you can imagine a real fight, only if you can perfectly apply locks or throws, there's no way to stop someone without atemi, a strong one, maybe even damaging the oponent.
No about my first question. Let's say the atack is shomenuchi, you do sankyo or kotegaeshi. If the atack is centered, the arm highly stressed, there's no way you'll do much, maybe a short irimi to continue his movement, like a soft block, of course step off the line, and then do an atemi.
Noone atacks standing 3 steps away, and keeping his hand in your hand. The normal reaction is to pull the hand when it's grabed.