I repeated all of these efforts adjusting here and there based on the initial results.
Heat treat: Fast ramp to 1425°F, soak for 10 minutes. Fast ramp to 1925°F, soak for 30 minutes. Quench between two 1" thick copper plates while blowing shop air in between. Both pieces measured 61.x Rc.
Spring temper: Inserted into furnace preheated to 1150°F, set point adjusted to 1100°F and soak for 2 hours once. Spring measured 47.3 Rc.
Blade temper: Inserted into oven preheated to 400°F and soak for 2 hours. Cool to room temperature and repeat. Blade measures 59.3 Rc.
I think this isn't half bad for my second attempt. It definitely helps to have access to nice furnaces and a hardness tester. Thanks for helping out.