Yes, Adam was a historical person. I think this is an important affirmation, without getting into how old the earth is and the exact year of Adam’s creation. Christians certainly differ on those things. But Adam was not selected from some pre-existing hominids and just differentiated from them because God created Adam after His image and likeness. I don’t believe that is viable from a biblical point of view.
In Romans 5, Paul suggests that there is an equivalence between Adam and Christ: as in Adam all die, so in Christ shall all be made alive. That doesn’t make any sense at all if Adam is fictitious but Christ is historical. The theological argument is that we are reckoned sinners because of Adam’s sin—that original sin is reckoned to our account because Adam sinned—and that doesn’t make any sense to me if Adam is fictitious.
So yes, Adam was a historical figure, and I would draw a line in the sand over that issue.