All good questions. With 8 episodes to play with and as good as these writers are, if they wanted it to go down this way, they'd totally lay it in correctly so it all makes sense. Off the top of my head, I'd have Jesse confide in Skylar about his worries about Walt in an attempt to help him and in the course of that conversation the poison comes up somehow, then later Skylar sees it ... and so on.
A good 75% of writing is getting from where you are to where you want to be, usually by working backwards. "Okay, so Davie needs to know sign language for this reveal to work ... Hmmm ... let's give him a deaf brother, that's the ticket!"