More importantly, neither Harry nor Ginny knew who Tom Riddle was. Anybody else almost certainly would have recognized the name Tom Riddle as Voldemort's birth name. But nobody was talking about V... Vol... He-Who-Must-Not-Be-Named. And as far as I remember, Tom did not introduce himself as "Tom Marvolo Riddle" until moments before revealing himself. IIRC, he'd introduced himself only as "Tom Riddle".

As for naming Tom "Tom", Dumbledore knew very well that invoking a name invoked power, and so it was entirely in character for Dumbledore to 1) weaken Tom by using his given name in his hearing rather than by the name of power Tom had chosen for himself, and 2) by attempting to nudge Tom back to a less malignant view of himself.

The core facet of the adult Dumbledore was his belief in personal redemption, he himself having experienced it so intimately. But I think Voldemort showed fairly clear (for a layperson, anyway), fairly early warning signs of being a sociopathic or psychopathic personality (lack of personal empathy, casual willingness to abuse people). As far as I understand psychotic abnormalities, they aren't especially self-treatable.

Dumbledore was absolutely wrong to hand him power without also seeing him treated (or at the very least diagnosed).

__________________
[Dr. Horrible]___________________________[Penny]
Listen close to everybody's heart________And you believe there's good in everybody's heart
And hear that breaking sound_____________Keep it safe and sound
Hopes and dreams are shattering apart____With hope you can do your part
And crashing to the ground_______________To turn a life around