Hey there from Madrid!
I am going to try to give answers to some of the questions on this topic:
1.- Rock in Rio takes place in Arganda, which is Madrid outskirts. There are buses which take you there (RIR) for free (showing your ticket) from Santiago Bernabeu Stadium. You can also reach Arganda by metro (but I don't know how far the metro station is from the venue)
2.- You can get tickets from February, the 23rd, only at El Corte Inglés (guess they will also be selling them online)
www.elcorteingles.es [69 € day ticket]
3.- A crowd of around 80,000 people is expected for that day, June the 4th.
4.- Concert time, never before 23:00.
5.- No other bands confirmed so far. Soon to be announced though.