Avira, saying someone is considered reliable isn’t the same as saying that they should receive מפטיר יונה. If Zucker wasn’t reliable, his sefer wouldn’t be used. It probably wouldn’t be on Otzar Hachochma either. A Conservative Rabbi can also be considered reliable. Jastrow’s dictionary is used by many יראים ושלמים and considered reliable even though he, too, was a Conservative Rabbi. And look how hard Zucker tries to escape the conclusion that Rabbeinu Saadyah was referring to Rebbi Yochanan, yet you still think he has an agenda!
But let’s leave Zucker to one side. You don’t accept his pshat in Rabbeinu Saadyah; ok. So can you suggest an alternative? Look at the Arabic original in Zucker’s sefer. There is absolutely no reason (besides wishful thinking) to assume the text is corrupt. So I challenge you to find any other way to explain Rabbeinu Saadyah. You can even leave out the words in square brackets if you like. Just explain the rest. Go on, I’ll wait.
I have already explained why the Ibn Ezra uses the term חסירי דעת davka here. I’m not going to repeat myself. But what is really stunning is your confident assertion, “The Maharshal doesn’t accuse him of not knowing Shas; that’s your own insertion.” Can you read and translate Hebrew? Yes? So how do you translate the phrase אשר לא היה בעל תלמודא? And then a few words later: והתריס בכמה מקומות נגד דברי חכמי התורה והתלמוד, או מבלי השגחה או מבלי ידיעה.
And what about the Avi Ezri, who understands the Ibn Ezra like me? Was he also a Conservative rabbi? And how do you understand the Ibn Ezra? Do you have an alternative פשט (other than R’ Shmuel Motot’s פשט, which simply doesn’t work)?
I, too, think the Oruch Hashulchon is a masterpiece. Indeed, I consider it to be one of the greatest seforim ever written. And I also pasken like him against the משנה ברורה. But that doesn’t mean everything he says is binding. You ask whether I would also argue with a פסק from the רמ״א. Allow me to answer you by quoting from the מורה נבוכים ח״ב פט״ו:
כל דבר שהוכח לא תוסיף אמתתו ולא יתחזק הנכון שבו בהסכמת כל העולם עליו, ולא תגרע אמתתו ולא יחלש הנכון שבו אם יחלקו כל אנשי הארץ עליו.