1) Incorrect mechanic by LJ for sure.
2) Technically, it's an IW, as the signal kills the play.
3) This is one we can (and should) just "steamroll" over because the kick crossed the NZ, nobody is trying to advance it, and the team behind cannot do anything else with the ball with it beyond the NZ. Replaying the down and literally following the rulebook would be the worst possible choice on how to handle this situation.
Now, if the ball was still behind the NZ, now we have a whole different can of worms on how to handle this!