What is a libreria de viejo and where are they found

It means old library or a place that sells old books.  They can be found in Paris as well as Madrid.  They usually sell very old and very literary works.  There is a big demand for such books for their high value and rare works.

answer; i believe the correct answer is (favorable balance);

originally he was supposed to be dead but they wanted to continue the series so they brought him back to life.