How do you know that? Hebrew did not distinguish between lower case and upper case letters. In fact the NIV doesn't capitalize "son of man"
and neither does the Jewish Tanakh
but it does capitalize "Him" meaning God as is obvious from the next verse in which He (God) gives him (son of man) dominion of eternal kingdom (the world to come under human messiah, as Judaism believes).
The OT speaks of nations knowing the justice (punishment, fear in OT terms) of the God of Abraham threough this son of man, and Daniel 14 speaks of the him (lower case h) receiving
It is eternal but not heavenly. Son of man never meant God in Judaism And Son of God never meant God in Judaism either.
he affirmed it by saying you say that I am and they understood that to mean he was affirming the title to himself
That's what the Gospels say but in reality that's no affirmation.
just as he did when Pilate asked him if he was King of the Jews, an eschatological title of looked for kingdom
Escathological in terms of delivering Israel from the hands of the Romans to the hands of the the Jewish King-Savior, not to a divine Person.
The messianic King of the Jews is a man, not God. His mission is to restore the Kingdom of Israel and establish world dominion. Notice, in Daniel it doesn't say the whole world will "worship" him (as a God) but serve him (as their Lord).
The word Son of Man (ben adam) means simply the son of Adam, a descendent of Adam, a human being, of Adams seed
“Daniel 7:13 it is used as a title for a divine person The Son of man.
“How do you know that? Hebrew did not distinguish between lower case and upper case letters”
There is only one place that bar enash (son of mankind) is used in the scripture for Son of Man and that is Daniel 7:13. In all other places “son of man” is a translation of ben adam. “Bar” is the word used for son in Daniel 3:35 for “son of God”, (bar elahh). That is why it is a title and not just a descriptive term, at least, it’s a good conjecture.