There two separate issues here.
1) Saruman's original plan
The Rohirrim wouldn't muster against basically their own king while he would be under Grima's influence.
Grima WAS keeping Eomer in check and all: things went smoothly before Gandalf.
I'd think the idea was to blitz Edoras and then finish the other lords.
2) Was Saruman out of his mind, sieging the Hornburg after Gandalf casted Cure Bullshit on Theoden?
I wouldn't think. That battle went smoothly NOT because of Gandalf or Aragorn or whatever, not really because of Erkenbrand either: but because of the Huorns (and later the Ents themselves). And honestly Saruman couldn't possibly have that intel.
What I think is that while he rushed things, 10,000 vs 3000 seems legit.
>He wasn't controlling him like a puppet, but it's very clear from the text that he was influencing Saruman's mind,
But that's the point: he wasn't "using" Denethor either, right? Or Pippin, for that matter. And Denethor was pretty much fucked up in the end, but Saruon didn't bother (ok, execpt making Denethor ostile to Gandalf, I concede that).
I dunno: seems more of a Second Age Sauron thing, to control enemy things. He didn't bother - hell, he didn't really mind control Gollum, who wasn't exactly the most powerful dude around, but had a thing for sniffing a certain Ring.
Eh, possibly. Gimli is the most superstitous of the Company, that's true.
Still, the Caradrahas really seem to fuck them up every time they try to walk more (doesn't it actually , and between the Watcher and Tom himself, the "aborigine creatures" seem relatively common in ME. My interpretation, certainly, but it does explain more than it seems (take the Eagles, for example. Who the fuck created them?).
Honestly I don't remember him saying THAT. He certainly seems self-delusional, not questioning why they didn't get at least a facebook post in 20 years, but I don't remeber him saying "there is no danger there". I can be wrong.