24.) If Dylan had committed suicide do you think that Eric would have gone through with the attack?
Yes, I do. Eric didn't really need Dylan except as a lackey who followed his orders. Eric was focused on his ultimate plan, and I don't think anything could have stopped him. If Dylan had backed out, it's possible that Eric would have shot him with the others IMO.
I am not sure what to think of this. I do believe that Eric was intent on killing, but Dylan was also feeding his ego by participating in the videos and drills for the attack. There's a slight chance that Eric would have lost interest if Dylan hadn't been there as a sidekick. If he still wanted to go with the attack, and Dylan had not been around, Eric would have had to go back to the planning stage and come up with a different approach (for example, it took two people to do the "triangulation" of the attack on the fleeing students which Eric planned as Act II, and he wouldn't have been able to get as many weapons inside for Act I if he had been acting alone). Without Dylan to help him, Eric may have postponed the attack, chosen another target, etc.
Another thing to consider is that if Dylan had committed suicide, his parents would have searched through his effects and would have found his yearbook, in which Eric had drawn the swastikas and pictures of corpses. The Klebolds would surely have been alarmed, but it's not clear that they would have recognized Eric's writing/scribbling. If they found actual threatening material about NBK, they may have gone to authorities, and Eric may have been investigated, but it appears that the most specific "warnings" about NBK were written in Eric's yearbook.
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Also, the question asks about Dylan committing suicide, not backing out. Had he committed suicide, Eric naturally couldn't have killed him. If Dylan had simply backed out, Eric would have had enough material written by Dylan (in his Eric's yearbook, etc.) that Eric the manipulator might have tried using this as a tool to force Dylan to act against his will and participate (with the threat, "or I'll kill you"). However, it gets complicated if we accept that Dylan wanted to die anyway; he might not have been susceptible to that type of pressure. Eric might, in the end, have killed Dylan, but this one murder might have derailed Eric's plans for a much greater attack if he had been caught and imprisoned for murdering Dylan, so I don't feel that I can make a good guess one way or the other what Eric would have done to Dylan if he backed out.