I've got the ultimate data for DLSS estimation.
The One document to rule them all.
NVIDIA DLSS is a new and improved deep learning neural network that boosts frame rates and generates beautiful, sharp images for your games - NVIDIA/DLSS
github.com
Can't believe it took me this long to find this even though looking up github repos should have been one of the first thing to do.
Massive thanks to u/oginer on Reddit for directing me to that document.
Gotta go to sleep, but tomorrow I'm fixing the calculator.
At a quick glance it would seem the current calculator is not that far off (at least for 4K, my assumption that 1440p was bogus turns out to be true),
but for 4K expect the fixed version to be more optimist (probably, I'd have to look into it more to confirm that).