Questions in Studying the Book of Faith – The Ontological View

Hello Rabbi!
I am starting to study your faith notebooks and would be very grateful if you could answer some questions that came to my mind while I was starting the first notebook:
I understood that Anselm’s ontological argument simply goes like this:
Starting point: God is the greatest conceivable being. No greater being can be conceived. Addition from Wikipedia: Anselm believes, like Plato, that concepts (such as “red” or “beautiful”) have a real existence outside of human imagination. According to this view, if something can be conceived (such as the concept of God), it is a sign that the thing has reality in the world.
Now Anselm makes an assumption that leads to a contradiction in order to show that it is impossible: Assumption A: God does not exist in reality. Assumption B: Existence in reality is greater than existence in thought alone. Assumption C: A being that has all the characteristics of God and also exists in reality is a being that can be thought of (simply think of something with those characteristics and that it also exists). Conclusion 1: A being that has all the characteristics of God and exists in reality is greater than God. Conclusion 2: A being greater than God is a being that can be thought of. Conclusion 3: There is a being greater than God.
It turns out that conclusion 3 contradicts the definition of God, since God, by His very definition, is the greatest being that can be thought of. If so, premise A has led us to a contradiction and must therefore be rejected. It is not possible for God to exist only in thought and not in reality. Final conclusion: God exists in reality.
First of all – I brought here the Wikipedia addition regarding Anselm’s Platonic view as part of the starting point from which he proceeds, it did not appear when you explained the argument in “True and Unstable” (where I used it to understand it). I think it is difficult to understand the argument without this addition. I wanted to ask – did you intentionally omit it from the book? In other words, is it not critical to the argument? (I think it is critical, because if it does not exist then what does it matter that a person can think of a being greater than God? It does not say anything about reality).
Let’s get back to our topic:
If so, I hope I understood correctly that Anselm’s (and the entire society in the Middle Ages’) starting point is that God exists and that nothing greater than Him cannot be conceived. In other words, the innovation in his argument is not the belief itself, but the actual existence of God in reality that is derived from belief: If you advocate, like Plato, that what comes to mind has some kind of reality, and believe in “God” (= the greatest being that exists) and that what exists in reality is greater than what is only in thought – this requires that He also exist in a real way in reality, because only in this way will it fit his definition as the greatest being (otherwise it would be possible to conceive of a being with divine characteristics and that exists in reality, which according to the Platonic view would teach about some kind of existence of Him, and that He would be considered greater – and there would be a logical fallacy with the assumption of the starting point that God is the greatest). Belief in God exists, but now we have shown rationally that the existence of God in reality is necessary for the person who believes. That’s all I understood.
And now for the questions:
1. What about the person who believes in God but disagrees with Plato? (I can imagine whatever I want, but that doesn’t mean it has any reality… Admit it, I’m not even sure I understand what Plato is saying, because I can imagine a lot of things that I think are very unlikely to have any reality, such as a flying spaghetti monster that decides when it will rain (a nice example from an atheist Facebook group I came across on Facebook))
2. And as a continuation of the previous question regarding the Platonic view – even if I agree with all the assumptions (or even just Plato’s approach), why not simply prove it by saying that it is possible to conceive of a being with divine characteristics that exists in reality, and according to Plato this would indicate a certain reality – and simply call it God?
3. What about the person who believes in God but does not agree that matter is greater than spirit? (“Perhaps God is so sublime that He does not have an inferior material embodiment?”).

And a general question following all the specific questions – I did not understand the division the Rabbi made when he explained that the above argument is not based on facts but on definitions. For the Rabbi said that it is impossible to disagree with the definition but only with the fact, and it seems that there is reason to disagree with this argument, as I showed above.
Additionally, it is impossible to ignore the fact that it is based on the fact that there is some divine entity (the argument proves that God exists in reality, it may be addressed to those who already agree that there is such a thing as God and convince them that if so, it must exist in reality through various definitions – but ultimately the fact that there is such a thing as God is a decisive fact in the argument. If so, this argument is also based on a fact. Isn’t it?
It came out a little messy, I hope the rabbi understood what I was trying to convey.
Thank you very much!