The whole point of the show is Walter isn't surviving bad guys....he is the BAD guy. He is smart, ruthless and totally insane. His true insanity is starting to come to the surface. Walter can or could have "gotten out" as Gus gave him an out. He wants in. This is the life he loves and this is the true Walt. The old Walt was the act. This is the true Walt.
I am not so sure about the out that Gus gave him. First of all, Gus told him that he was going to kill his brother in law Hank, and if he intervened, then he would kill his family. That is not a very attractive "out." Walt then went to see his lawyer so that he could make arrangements for his family to disappear, and from there went home to get the money. But Gus apparently already had 2 hit men waiting for him. That hardly seems like an offer to let Walter leave the business either. It seems to be an unexplained contradiction in the story line, because if Gus intended to kill Walt, then he surely could have done it when he had him in the desert.
That's what it appears, but since he has chemistry background he's probably smart enough to know how much dosage can be used and not be fatal. But it's preventing Jesse from knowing is another matter.
Yes, the evidence points to Walter, given his chemistry background. But I am wondering what happened to the poison Jessie had in his cigarette pack. It just disappeared. Walter did not have access to it. But Gus and his guys could have removed it just as Walter suggested. And Gus does have a history of killing children. Walter's inner bad guy seems to be coming to the surface, but he hasn't gone so far as to kill children, and it is not clear how he could administer a dose that would make the child ill but not kill him.
Walt is a manipulative motherfucker. He manipulated Jesse to kill the other chemist and became untouchable in the end.
Everyone is really down on Walter around here. LOL Walter agreed to kill the other chemist, and was going to do it. But he got picked up be Gus' guys before he could do it. The only chance he had to save himself (and probably Jessie too) was if Jessie killed the chemist. Its not like Walt was in control of the situation and manipulated Jessie into doing the dirty work.
For sure it will be interesting to see where Season 5 takes us. Mike getting out of the hospital should be an important part of the plot. Maybe Mike will try to kill Walter. Or maybe Mike will become Walter's partner and handle the distribution of the product. Walter and Jessie haven't a clue how to market what they make.