The simplicity of disproving the claim that jesus was God and man is just too simple. I hope I can answer this question to your satisfaction. It is important to note that Christians invented this term Hypostatic Union at the First council of Ephseus. It is just a label they used to explain the unexplainable.
Whenever you have a discussion on a controversial topic you have to define terms. What is God and what is man? God is all powerful, without beginning and end. Man is not all powerful because he has limits, man is born and dies, therefore how can someone, anyone, be God and man.
The concept is full of contradiction and intellectual fallacy. It is like me saying I am you and me at the same time. Is that even possible? no. I am either me or you.