Why x=x ? I see your problem now. But once again, I understand this is a philosophy forum, and in that vein it is true that we look too deeply sometimes, especially with such kinds of ontological questions.
You are pretty much correct but why is x=x a problem? Sure x = a number of combined variables. But that also means that x is a particular thing. And no other thing is that particular thing so in making this distinction we must also accept that x is unique; x is itself. Which, again, can be a culmination of other variables, maybe infinite amounts. It is easier and still works formulaically to use the shorthand, x=x. If x were not equal to itself then a harder question would arise: "Does x exist independently of itself?"
My biggest question to you is "why should x=x be something you don't already know?" That's the point. I brought biology into the conversation because of its relevance to corresponding mathematical models. x=x is obvious to us because we evolved for it to be. Otherwise we would not have survived in the same way.