Eh... On the messages being hard to understand, the most important bits were more clear.
-Harper is a bomb he can make go boom at the snap of his fingies
-This is an antidote to stop that
Like yeah, there were some unknown consequences to taking the antidote, but if you don't take it and you meet Longcrier, you're dead. I felt that was very obvious.
That said, sometimes players are dumb and you can throw them hints. Michael did a pretty good job at this I think. "So to be clear, this is a big thing and it's possible for people to die here. Just want to make sure you're aware of that." "Haha, yeah totally. So let's have Longcrier walk into us and then we just fight him." ._. "Okay, so to be clear, your plan is to lead him out... and then you're all just going to be there. That's it, right?" "Yeah! But like we'll make him think that he was led by that dead guy." ._.
Only things Michael could do were give the sort of insight or history or whatever that "You remember the first clip again" and replay it if they score well or give a dex saving throw to try to inject Harper in time, but it'd be a hard check at that...
From here, I expect a new character from Tim or for the party to go on a quest or do something to get a True Resurrection spell.