I don't think it was Ancelotti's tactical fault on the contrary, Real Madrid were able to control the ballposition more and play much better but they were just unlucky in the first leg of the Copa Del Rey against Barcelona.
Real Madrid did have not too bad match and they created some opportunities to get goals but unluckily they did not score any goal. They have good enough performance to give them belief that they can beat Barcelona in a second leg and win in aggregated result.
About confidence, I don't think I can find any club that have very solid confidence about themselves like Real Madrid in a long history as well as in the past two seasons. All challenges they passed through to win Champions League in the past season prove a lot about their confidence and ability to beat biggest opponents.
and for the second leg later I think these two teams still have the same chance to beat each other, in fact I think the percentage of these two teams is still 50-50.
With Real Madrid, until the final whistle, don't say you are winners against them.
and it is true that since Xavi has coached Barcelona there have been very many positive changes that have occurred and especially in this season which has made Barcelona at the top of the La Liga standings temporarily.
Xavi has been doing his great job and has brought big improvements to Barcelona but he has to go too far to achieve what Carlo Ancelotti has gotten in his career. Winning La Liga and Coppa del Rey in a same season will be a milestone season for Xavi management career.