so flash has a nervous breakdown and that causes him to jizz speedforce all over other heroes and that kills them?
why did he have a breakdown?
Flash struggled with the idea of Sanctuary and thought it might be a fake thing to placate him (other heroes going "no bro, we get it, we get it, we've all been there") so to understand whether or not he was alone or other people got it, he attempted to experience everything that every hero who had used the facility had ever gone through in the span of a moment, only to find that watching every traumatic confession a thousand other people had gone through was actually way too much, lost control of the speedforce and killed everyone nearby who had come out to see what was wrong.
why did he frame booster and harley?
why did he travel forward in time to meet future self. was the future self trying to kill him or vice versa?
He killed himself to punish himself and try to atone for what he had done, he framed the two survivors because after killing himself in the future, he needed time before Batman and the rest of the JL came to arrest him to try and make up for the wrong himself (by killing himself and leaking the Sanctuary situation to Lois). The idea was that he'd loop, kill himself in the future, atone for a few days and then die at his own hands--but instead he was interrupted and convinced that more violence and death wasn't going to solve the problem, so ultimately he was arrested and a cloned body was used to fill the paradoxical missing slot.