would there be any truth to this theory 
Clearly not, given that he now just looks like an older version of the same kid, and he's getting jaw surgery and implants done.
Wolff's Law would be correct in so far as it applies to bone adaptation at a
microscopic level from an increased physiological load. However, hammering away at your face with some stupid object would not lead to growth significant enough to protrude through the soft tissues, and even if it could, the fractures wouldn't heal in a uniform manner so you'd just look malformed.
The only thing this guy was doing was documenting his stupidity on film while damaging his skin.
