Flick shouldn't have complained much about the players not having enough rest time before the kick off and all that even if he's right I see no stress in this game only if they're to play against Madrid or Atletico Madrid tonight that is when he would have start up a protest.
You can see that he made a point of complaining about the schedule because one of his players got injured. Olmo is a very important part of his squad, but now he's injured and will miss games against Dortmund and Atletico. They have to fight to make sure he will be available for the second leg of the Dortmund game. If the game had been played on a later date, I'm sure he would not have gotten injured.
Real Madrid will be hopeful again, if they can win the next El Clasico match because that's where they have their next chance. If they fail to win that match, Barcelona will win the league. Currently, I don't see Barcelona ready to lose any of their upcoming matches in Laliga because they are after winning the trophy.
Before the El Clásico, they have to make sure they don't drop any more points because it will be useless for them to win the El Clásico when they have already gone 6 or 7 points behind Barcelona, because looking at the form of both teams, Madrid looks more likely to drop points.