The Greek for "one" here is hen, as opposed to monos, which means one numerically. The word hen can mean numerically, but it can imply a collective one, as in 'one people', united as one. Jesus is saying He and the Father are one, in that what He says and what He does is what the Father wills. This, of course, can be read in a moral sense, to imply divine endorsement, 'I'm just a man, doing the right thing, and I have God's backing because I'm doing what He would want me to do' – but if that is the case, the Judaeans would not have sufficient grounds to stone Him, because that is what they would claim for themselves.
I do not understand your reasoning in bold.
Let’s pretend to be the scribal elite for a moment. Let’s assume they understood Jesus correctly. In John 10.33, the opponents accuse Jesus of making himself a god. As we know, the Greek word
theos is tellingly used without the definite article.
In the 1st-century Jewish context, there was a category for divine mediators like Jesus that I have already mentioned above (like the Angel of the Lord, Metatron, Moses) who bore the divine name and exercised divine authority. So let’s assume the scribal elite understood Jesus to be claiming this kind of status.
Jesus quotes Psalm 82.6, “I said, you are gods,” in order to show that the Law applies the term
elohim to humans. If the Law calls humans gods, then his claim to be the Son of God should not be considered blasphemous.
Claiming to be a god pretty much warranted the same treatment as claiming to be the High God: execution by stoning. The authority of the scribal elite was based on their role as the authorized mediators of the Law and the voice of God. If Jesus is the authorized bearer of the divine name, his commands carry the weight of God Himself. This renders the traditional religious hierarchy redundant, unnecessary, obsolete. The claim to be a god
displaces them and removes their authority over others. Their entire judicial and spiritual jurisdiction is at stake.
That Jesus guy has to go, they reason. This is clearly not just another debate on
halakha.
“Pay attention to him and listen to what he says... since my Name is in him.” Remember,
“he will not forgive your rebellion” (Exodus 23.20-21). As this powerful agent, Jesus holds the power of life, death, and spiritual standing. The scribal elite only have two choices: submit to this agent or eliminate him. If he is the one they must listen to, then they are the ones who must be silent.