Questions about Labyrinth of the Spirits

I finished TLoTS a few days ago and realized I have some lingering questions about some of the subplots. I devoured this book pretty quickly so I wouldn't be surprised if I missed a few key details.

Spoilers for the whole series are ahead (not just Labyrinth), so proceed with caution. Thank you for your help!

!1. I don’t get why Rivera killed Salgado. He took Salgado’s treasures but just kept them in his creepy mannequin lair, and it wasn’t even that much treasure? How did he even know about Salgado and why was he on his trail? !<

!2. I'm also confused about the sequence of events that had to do with Valls and his disappearance. I know the general idea was that his true enemies were his ‘friends’ in the government, but then… Leandro told Alicia he had just wanted her to find Valls, but not investigate his past. Well, before Alicia and Vargas were taken off the case, Valls had already been kidnapped by Hendaya. But Hendaya WORKED for Leandro… so why did he have Alicia on the case when Hendaya had Valls from the beginning?!<

!3. Was Leandro really Valls’ partner? In that case, there was definitely a better way to find Valls (with Hendaya) and there really wasn’t a point in getting external people involved that were separate from the government’s corruption. !<

!4. Why was Leandro disappointed in Alicia for discovering more about Valls (during their confrontation in his hotel room in Madrid), and why did he expect her to not dig into anything? I feel like I’m missing some key context here lol. Personally, it seems pretty obvious that if you hire your best detective to investigate a disappearance, the first thing they will do is find out everything they can about that person’s past. If it was a sensitive government matter that they didn’t want to come out, why didn’t they just leave it as an internal investigation, especially since they have a lot more context on Valls and his past? Was Leandro just blinded by his affection for Alicia and trusted her too much, or maybe underestimated her abilities?!<

!5. Also, if Leandro’s goal was just to prevent all the government’s crimes from coming out, why did they even keep Valls alive and rotting in his cell? A simple explanation for this is that they wanted to make him suffer and have a slow death rotting in his cell (which made for a poetic ending for Valls), but Leandro seemed uninterested in everything except hiding Valls’ crimes, so killing him immediately would’ve made the most sense. !<

!6. In Prisoner, it was mentioned that Valls was keeping David around because he suspected he knew the location of the Cemetery, and this was never explored further. Why would Valls want to know? Was this just the classic power-hungry government person trying to destroy books?!<