Re: So . . . . .
It basically consumed 3 x our sun's mass in an instant,
Various reports seem to have muddled this aspect.
I'm not sure that the process 'consumed' mass, certainly not in the form of a nuclear reaction or suchlike as some reports seem to suggest. Wasn't it simply that the kinetic energy which the two black holes had accumulated as they attracted each other to travel at something like half the speed of light went into rotational kinetic energy when they got close. Much of this was then radiated away as gravitational waves as the pair of them did their final twirls in a closer and closer embrace before they coalesced.
The radiated energy was equivalent to three sun's worth, but the mass that was lost was the relativistic increase in the black holes' masses due to their high speeds, which they gave up when they stopped each other, rather than conversion of the matter that comprised them.