#2
no because the locking nut is way thicker that a normal nut, there would be too much exces room to fill, you could always just leave the actual clamps off and leave it like that.
#3
hmm, so how can i go around making space for it?

How about filing the fingerboard from the headstock so that it fits?
#4
oh right you want to install a locking nut into a normal neck (not routed for a locking nut) I'm assuming then you have a bridge with fine tuners then, floyd rose, kahler etc? or are you just looking for extra tuning stability? if you want it to hold tune better just look at some locking tuners.