And no one said you can’t ask questions to gedolim; emunas chachamim does not mean to not question, as you said, it means that you listen even after you question, and even if you’re not satisfied with the answer. This is what we do with chazal, rishonim, achronim..we ask kushyos on everyone, but we don’t say that they’re wrong because of those kushyos.
And how exactly do the Rambam and ramban not “pasken” like rashi? He’s not discussing the halachos of toleh al beis din; this is a complete misunderstanding of the issue.