Sure, so long as he isn't misleading shareholders - and that generally requires fraudulent filings. I'd say that he is much safer pumping the stock than he was, almost exactly a year ago, when he very publicly stated that he thought the stock was overvalued.

Saying things that impact the stock price is a normal part of being the CEO. EX: Drug X failed/passed clinical trials.

The limitation is on manipulation of the stock price more so than simply releasing information.

It depends on if he actually is considering privitising at $420. Stock manipulation requires an "artificial" price.