Changeling (film)/WMG

Walt is Walt Kowalski.
Their ages don't quite line up, but 10 years or so isn't that far to lie about your age as an old man. And that other kid who got kidnapped in The Fifties also turned up in Michigan...

Alternately, Walter is Walter Sullivan.
He was taken into wish house and so thoroughly brainwashed that he believes his mother is an apartment. (Could be the trauma from being held by his kidnapper.)

Alternately alternately, the original Walter Sullivan did commit suicide in jail, so the cult kidnapped some kid and brainwashed him into believing that he was Walter.

Makeup deliberately invoked an Uncanny Valley appearance for Sanford Clark.
They did this by not quite covering up the birthmark on Eddie Alderson's eyelid, creating a "can't quite place it but something's wrong" effect around the eyes. Sanford Clark didn't have one and it's easy enough to completely cover on a Soap Opera shooting schedule, so it was probably thrown in deliberately.