Most of this looks good, but I have a problem with the Kalani talks about the Pipin Murder. For him to do that, he would have written it down before shooting Pippin. Pippin is shot in the AM and they Kalani Kamakazies that evening.
However, when they touch down on the roof, Kalani can have a few moments to confess, but he is really pressed for time to 'get to the choppah"
According to the unofficial/slightly official in some cases timeline, there's a full day between Pippin's murder and Kalani's suicide. There would be a lot of downtime in 24 hours sitting on the tarmac to write a confession. It could also be easily implied by his words what he was planning on doing, and then the readers fill in the rest.
Believe me, I have been one of the largest proponents of Kalani had no chance to stash the journal...but the possibility is there. He could have sent Riley down much earlier than he said he did, stashed it, and went back to the roof.