The quotations provided does not necessarily mean they are correct English. You have not quoted an English grammarian or teacher.
The sentence He wants to know if you will be here tomorrow is in reported speech and it contains a conditional sentence , i.e. if you are here tomorrow / if you are going to be here tomorrow. Yet, if you are here tomorrow is correct English, if you take into consideration the fact that the present tense simple has, among other uses, the one which states a future action.
I usually follow the rules of English grammar. Let`s hope that the English teachers on this site will give us some advice or opinions on this.
Anyway, I like the way you try to demonstrate that you are right. I don`t say that you are totally wrong. Let`s wait for some English teachers` comments.