Hi Everyone. I know that now it's being a clear evidence that Walt did poison the kid (Saul's confession is a fair enough final evidence). Period.
So I'm posting this just for the fun to have discussion about all of this and point out how I think the complexity of this plot event was made on purpose so as to make us all wonder about it.
So I first started buying the idea of Walt poisoning the kid because all the elements you quoted deffinetly accuse him. And I personnaly never questioned the psychopathic tendencies of Walter. He is clearly a goddamn lunatic freak with frequent and very random murderous envies. No contest.
That being said, he is also a perfect liar, manipulator but more than anything a very good calculator. And I insist on this last one.
As a graduated and brillant chemical professor who turned completly mad and unpredictable, all his success nontheless remained in his calculator skills and obsessions.
So, on this simple point of view, until we were definetly conviced by Saul's words : what reason would he have (as he stated himself in a very desperate moment) to poison Brock ?
So as to make Jesse believe that Gus did it ? But that's clearly not logical at all. Because if the point was to kill the kid and let accuse Gus, why poisoning him with Lily of the valley ?
So it appears accidental ? But then that don't accuse Walt nor Gus...
So what's the point ? Why wouldn't he have just poison him with ricin ?
Because that accuses Walt too much ? But then why getting Saul taking the cigaret off the packet ? So Jesse believes that Brock got poisoned with ricin ? But again that doesn't accuses Gus at all, that accuses Walt ! And there is absolutly no reason Gus did it.
And I really believed that Walt believing Gus did it was actually the fruit of his sincere and personal paranoid tendencies. And I thought this is why he laughed with despair. Just like he did when his wife told him about his money being offered to Beneke. Know I must confess I think he's just an evil master mind and a crazy nutcake.
All of this really didn't make sense at all.
And I still think the whole point was making us, as spectators, wondering about all this mess despite of the evidence. Because playing with our minds is pure fun.
According to my theory nobody had no reason ever to poison Brock and it was really more logical he just got intoxicated accidentaly, and all the surrounding elements were intentionnally put in our sight so as to make us elaborate paranoid theories.
Think about it : why in the world would such a calculator as Walt put all the potential success of his plan remaining in the very low probability that Jesse suspect him and then buy the crazy story of Brock being poisoned by Gus ? For what reason ? Why the hell would Gus even poison this child ? I mean, either Walt is an unpredictable crazy fuck who just tried the last desperate mad stuff that crossed his mind, either he invested it all on Jesse's weaknesses. That is to say the way he got easely influenced, and his original loyalty to Walt.
Here is why my theory is that Brock's intoxication was made to look like pure Deus Ex Machina, even IN THE END, it finally appeared to be what it is : a volontary poisoning.
End of my pleading.