US copyright law doesn't allow for protection of something like that. A dingbat, yes, but if it's very plainly recognizable as an X then the exact shape and output of that typeface isn't protectable. You can even print out a font, scan it, and create a new copycat font from it. The only thing you can't do is reproduce the actual typeface file itself, which is fundamentally a single copyrighted piece of software. Some other countries allow more protection on the shapes of individual letters, but I don't think you'd ever win a case anywhere on such a simple geometric shape as this X.

Not really; the XOrg logo is clearly designed in two parts, with a break between the two sections. It's absolutely reminiscent of it, though, just different enough that you can't really call it a copy.

That's just privacy protection. I own a few domains, and none of the whois information points to me personally.

Unless it's since changed hands again, he did actually buy the domain back from PayPal ~6 years ago: https://www.techspot.com/news/70077-elon-musk-buys-back-xcom-paypal.html

It's why x.com currently redirects to twitter.