Re: Wilt Chamberlain free throw dunks:
The articles and pics in the OP do not constitute a proof (that would be live footage during a game) but they provide strong indications that Wilt did indeed do this. I mean we have newspapers mentioning rule changes and several live accounts. And of course seeing his leaping ability from other videos it doesn't sound unreasonable at all. In fact I'm 99% sure that Wilt could dunk from the free throw line.
However... that doesn't indicate that such a strategy of making free throws would be viable in a game.
1) He'd need to take off from behind the line. If he stepped on the line he would commit a violation. He would have to practice quite a bit to take off at the right spot.
2) He would get tired dunking the ball from the FT line 10-15 times a game.
3) How would it work on the second free throw when the defensive players would enter the lane to get a rebound?