Can I rez "Experiental Data" after opponent pay for using icebreaker, to increase the strenght of encountered "Wall of Static"? Opponent will be missed strenght and run the end with the opponent lose credits?
The same with the Nisei MK II - can I end the run after opponent pay for using icebreaker but befor opponent pass encountered ICE?
You can rez Experiential Data after the opponent pays to use his icebreakers, but all the routines are already broken so it will have no effect on that Wall of Static. You would have to rez it at the same time you rez the ice (or when the runner decides he's encountering the already rezzed wall) for it to be useful.
Nisei Mk II can be used any time paid abilities can be used. Usually this is after passing all ICE (and paying the credits to do so) and after declining to jack out, but just before accessing any cards.