Busy night!
It's an interesting question, but you'll hate my non-answer answer...
I don't think he's a sliding scale cat. If anything I would prefer you take a reduction to get something that is consistently shootable over 250-ish. If you find over the course of a week or two that makes things worse, then could always try a sort of sliding scale.
He was still in very safe numbers last night, without the carb intervention probably would have ended up right around 90 anyway.
The other interesting thing is had you shot closer to 12 hours apart, he probably would have been above 300 anyway, just not sure how much cushion that might have bought you.
He seems to follow more of a Lantus pattern, where if he's relatively flat yellow leading up to preshot, that's when you get a more active cycle following it.
So, long story short - up to you! I think it would be better to reduce and try to shoot that above 250 or so. But if you want to try a sliding scale, not a problem...but I think you'll need to take the trend leading up to the preshot into account. That's a 3rd option I suppose, when he's pretty flat and ends in a yellow preshot, reduce by maybe 0.25-0.5U.