In this case, I guess I’d treat it as any other fantastical statement: extraordinary claims require extraordinary evidence.
Ah, so this conversation doesn't matter. You made up your mind even before you even asked for explanation.
By design, philosophical concepts neither require nor can produce proof. If they could, they literally wouldn't be philosophy. If your idea of arguing how "you" exists includes the line of reasoning that you need proof, then the truth to you is that "you" don't exist, because you cannot prove your consciousness to someone else either. Just the same as I cannot empirically prove my consciousness to you. You are an amalgamation of chemicals and genetics, as you said.
So really, one taking your stance doesn't have the conversational authority to even ask what proof is there. The hard evidence is just chemical reactions and genetics all the way down.
In any case, all three of the concepts I listed are not my ideas. They are debated topics, some for literally centuries, in the philosophical world. If you suppose yourself better than the likes of Plato or Socrates because you think you can label a fundamental aspect of the universe as a "mistake" people make when they think about it, then there's really no honest way you can even approach theories like those without immediately discrediting them.
I guess have fun with that. But for me, there's no point in contemplating with someone who supposes that proof precedes basic concepts of philosophy in a question inherently about philosophy.