Both are now unsupportable. I stipulated to them in the past despite observed material disappearance effects, but now that we officially have repeatedly-demonstrated Trek-like non-thermal non-mechanical vaporization (known elsewhere as POOC'ing, i.e. "phasing out of the continuum"), such estimates are no longer acceptable.
Some or most of Alderaan's mass is rendered absent without apparent conversion to energy . . . it just goes bye-bye . . . ergo gravitational binding energy and 1g presumptions are not a valid tool.
Star Wars isn't hard sci-fi any more than Star Trek is. Trying to shoehorn it into being so is more absurd now than ever. Or to put it another way, if you'll forgive the phrasing, we can pretend they're hard right up until the point where they go soft on us, but when they go soft we need to stop pushing, because it's neither of use nor of pleasure to anyone.
Or, the short version: