I've some how missed this thread till now but it's made fascinating reading and congratulations on hardening your first blade.
Please feel free to ignore my little walk down memory lane below...
I used to work in a lab making weird and wonderful ceramics (mostly superconductors) where the firing temperatures were well over 1000 deg C. quenching from those sorts of temperatures is scary! We used long tongs, a face shield and special heat proof gauntlets to take things in and out of the ovens which were never allowed to go below 900 deg C. I seem to remember the gauntlets were rather expensive but they did the trick. I only remember feeling any heat once when I had to take something out at 1350 and the gloves started smoking!
As for quenching we did use liquid nitrogen but it was hard to get a good quench with it. The problem is it's not very wet and it vaporises rather easily. Water was probably the best we used. We never tried oil because we didn't want to contaminate the samples. We also didn't swirl the samples about we just dropped them into the liquid, they were held off the bottom of the container by a wire cooling rack. Of course we weren't interested in sharpening the samples afterward...