Law Confusion

In yesterday's Bundesliga match between Hannover 96 and 1899 Hoffenheim, there was one confusing situation which is not explicitly clarified in FIFA Laws of the Game.
You can watch this situation which led to the first goal for Hannover 96 by watching the adhered video (from 1:20):

Was this goal regularly given by FIFA referee Thorsten Kinhöfer?

In "Law 13 - Free Kicks", there is no information revealed about this specific topic. Kinhöfer said in an interview after the match that he did not see any infringement. In addition, he stated that he asked the Hannover player Schlaudraff whether he needed a wall or not, as Schlaudraff denied this question, Kinhöfer released the play but without using his whistle.
Consequently, there have to be three questions on their answers the whole situation depends:
- Was Kinhöfer allowed to continue play without using his whistle?
- Has the player who takes the free-kick the right to decide on whether the wall has to be placed or not?
- The fact that Kinhöfer showed the players his whistle which means that everyone has to wait for his signal, does this fact make void the opportunity of a referee not to use a whistle to restart play?


First, we have to consult the Referee Guidelines of Law5 (Referee Signals; FIFA Laws of the Game page 78):

 

Consequently, it is a wrong decision, isn't it?