Star whereas Vader was not part of the military command structure- he was representative of the Emperor. This gave Vader a lot of freedom that most Death Star senior officers resented, but Tarkin understood Vader's worth. Vader also respected Tarkin, incredible given his usual temperament to most Imperial Officers.

I don't think Tarkin knew Anakin was Vader but I think he knew that he was once a Jedi. Tarkin doesn't really like Vader, IMO, and I think it shows how he dismisses the 'old religion'.

Bail Organa certainly knew. I think he made sure that Leia would be ready to face the Empire as best she could. Out of the whole galaxy, I think only 4 living people knew the absolute truth.

The Lars... they may have been told at somehe got to the Death Star in ANH.

Bail figured it out, in that Darth Vader book.
Even if Obi-Wan didn't know Vader was alive by the end of ROTS I'm pretty sure he figured it out when he caught the first news holofeed with this guy named Vader standing around beside Palpatine

Which was in the "Darth Vader book" you mentioned- Dark Lord: The Rise of Darth Vader.

Though I suspect that Bail knew in RoTS. In the aftermath of the fight on Mustafar, Yoda and Ben may have filled him in on the details- so when he sees a suited "Darth Vader" not long afterward, he knows exactly who it is.

But is Vader even in an official role? He's basically a henchman... he has no official role as far as