Crank Torque Conundrum

Leave it alone. Not that much over-torqued, or the bolt would have sheared off as it stretched.
Usually a safety factor of 2:1 on such torque apps.
Your hex bit was made from 'cheese-like' material, BTW.

London IMechE prof. / habitual grease munkey!

That's the kind of news I want to hear ! I celebrate confirmation bias.

The hex bit actually broke, rather than rounded out, I'll take a picture, it was one of those "Oh shit, what have I done, I can't look" moments, lots of grunting, lots of force, then suddenly a loud cracking noise and loss of tension, I was glad it was the hex bit rather than the crank / crank bolt / BB thread or any of the good stuff . . .