No, Saul knew that Mike was connected to Gus. That's how he got in touch with Gus. As as Mike himself told us, Saul is and was well aware of what kind of man he was, else his threat wouldn't have held as much weight.
It just seemed fairly evident, in that last appearance, that Saul hadn't realized how in over his head he was, & what type of people he was dealing with, regardless of how connected he was with them, & therefore wasn't informed enough to realize how screwed he might be by aiding Walt & Jesse
And was Gus on the knife edge before Walt? I must have missed that. I thought he was doing fine without Walt.
He was, but Heisenberg's involvement with the murder of Tuco, fouled it all up. Gus intervened, & protected Walt, from Tuco's cousins, & that led to their deaths, which I imagine is a major issue with the cartel, as well as the fact that the last time we saw the leader of the cartel, he was getting his HQ stormed by authorities, who I assume were tipped off by Gus, who was making his move, by taking both actions
Gus saw in Walt an opportunity to get clear of his dependence on the Mexican drug cartel, & chose to protect him from retaliation, in order to profit from him, which tells us two things. Gus was using his new found meth specialist to change the balance of power, & also that Walt is a rather rare commodity, in this equation, or Gus would have made this move to out maneuver the cartel with some other chemist, like Gale, for example
Make no bones about it. Walt is the goose that lays the golden eggs, & true that it won't hold out much longer, but it has managed to get him this far, & it might have a bit more juice to get him an upper hand, in some way, if he plays his cards right, and is as clever as they seem to be implying he might be
That scene with Mike infiltrating the chemical supply company had a double purpose. First, to show what a bad ass he is, & second, to show that the cartel is probing for weakness. A shutdown of even minimal proportions, in production would be such a sign of weakness. In fact, one of my favorite things about this show, is that all the conflict that has developed is directly connected to Walt, & his choice to become a criminal. Jesse's become a murderer, Hank's been crippled, Gus is facing a drug war, & wide variety of folks are getting dead