I don't have Stewart at hand to check your claims that his proofs are rigorous (I sold it), but as far as I remember, it is not as rigorous as, say, Courant and John, and I don't recall Stewart's "rigour" helping me any when I read Courant and John.
Indeed I read Stewart from cover to cover. Yes I read his proofs, but I never paid much attention to them. The truth of the matter is that Stewart's "proofs" are not an integral part of the text in that one could leave them out entirely and still be comfortably able to work through the text. Could you say the same about Courant and John? No, the focus of Courant and John is rigour, whereas it is not in Stewart's book. Just compare the questions in the books, for example. Stewart is mostly about "compute this integral", whereas Courant and John's questions are more theoretical and proof-oriented.
I think we agree Stewart is not enough preparation for baby Rudin. Like I said, Stewart's Calc book is not more sophisticated than a pre-calc book, so how it prepares you for Rudin, let alone Courant and John, I have no idea. We both agree that a book like Courant and John or Spivak is a necessary prerequisite for Rudin. Yes Courant and John will be a little harder for the noob, but it is necessary to read. And I still do not see why one should read 1000 pages of Stewart before Courant and John, since it never helped me at all to read Stewart first. And reading the chapters on vector calculus in Stewart's books are a complete waste of time. So you're saying it's necessary to read Stewart AND a rigorous calc book before Rudin? I did this and I can vouch Stewart was a 1000 page waste of my time. If a book lke Spivak is necessary, why waste the timewith Stewart first, when it doesn't help at all? It only teaches the mechanics of calculus.
Btw, I read Stewart because I was forced to, and this was before I knew any better, i.e. before I knew there was such a thing as a rigorous calc book.
And many students have had Courant and John or Spivak or similar books as there first calculus books. Indeed, those books were written for students with only pre-calc and no prior exposure to calculus.
But like I said, if your heart is set on reading Stewart, go ahead, but get an earlier edition, which will save you $$.