If I got this right. They are trying to prevent the explosion by having Seo undergo a near-death experience and also catch school president in the process. Like what has been discussed in the recent chapters with cause and effect. But I am suspicions that Komachi is the one trying something funny there regardless of Seochi's outcome.
Prez plans to kill Seo in hopes of that satisfying fate and cancelling the explosion. This means Seo's death is guaranteed to come first. But as soon as Seo is saved Satsuki is also going to have to stop the explosion in her own way.
Since all of Prez's murders so far have been extremely hands-off—manipulating probability to create near total accidents—they have to force him to take direct action, righting the course, if they want to catch him guilty. But Miho is kind of tipping her hand here; the one outlier murder was Miho burning to death, which took some very direct methods manipulating Michiru. Of course Miho knows Seo was behind that one so she has Prez's M.O. figured out. Miho might be the most impressive character with her growth and consistency as the most attentive of the gang.
Anyway, if the manga wants to take a twisted route, Seo/someone will die but the explosion will still be happening, disproving Prez's theory. And there are 2 major wrenches the characters aren't accounting for: Seo's bully victims and Komachi. The former are definitely planning something and could accidentally kill her on top of Prez's attempt, and the latter is just the eternal wild card. If the explosion is the scene from chapter 1, she's almost certainly behind it.
While there's a couple reasons to think we're in the home stretch (chapter 1 and chapter 58 referring to a final storm) I'm not so sure it'll end that abruptly. There's still lots of mysteries and subplots to resolve, and that shouldn't instantly put a stop to the deaths or Satsuki's concerns. To compare it to Ryoko's previous work, Shi ni Aruki, I think the explosion is more like the point the killer was identified. We might get some real answers as to why everyone's dying, but there was still a lengthy arc afterwards and a few chapters of epilogue after that. It doesn't feel like Liar Satsuki is in a hurry to wrap up so hopefully we get the same treatment. At the very least we've got another ~11 chapters for volume 8.