True plus every indication is that he was very close to his parents - even if he wanted to break away for a time, you'd think he'd make some contact with his folks so they wouldn't be panic stricken.
As far as making it on his own, even if he had a sheltered background, I can see someone just going for it. At that age the sky is the limit and sometimes you feel like you can accomplish anything. When I was much younger, I moved into a cabin in the woods with my boyfriend. No electricity, running water, or toilet (just an outhouse). We just made due and found ways to get things done. Be resourceful. Of course living with a roof over your head is a step up from being on the streets, but still if a person has the motivation, they find a way.
IDK, even though it's a possibility he never made it out of the park or near the park, I still think there's also a chance that he did and he's out there somewhere. I don't believe that in most cases, but this one has so many twists right before he went missing that anything is possible to me.