1. there is a "tag" on the minimap in his secret room saying "skillbook" for me (prolly a secret a baught) - but there isnt anything there, how do i grab it.
You sure you haven't grabbed it already? IIRC, Maradino's ghost spawns after you gain access to his secret room. Skillbook in question, along with Blood Stone and Maradino's Secret Files should be right there, lying on a table in plain view.
2. i was told by a buddy that the troll king cave is empty because it only triggers when i go with Maradino, did i mess it up by killing him?
No you did not. You don't "go" anywhere with him, you only kill him right where he shows up (well, unless you flee from combat). A way to access the Troll Cave is described in his secret files.
3. did i miss the famed portal puzzle?
No you did not, it's a bit further into the game, after you've passed the Immaculate Trial.
