I don’t measure heat, mostly use hot water from the tap, heat until you can bend easily, usually too hot to hold in your hand. If you need to, reheat.

You are over-thinking it. Hot enough to bend. A heat gun is inexpensive, can add extra heat quickly to spot bend, tweak.

Once you have cut to shape and thinned, they heat and bend easily. For example, a scaled razor with slightly bent scales can easily be straightened by heating under running hot water, 2-3 minutes and shimming the open razor with3-5 tongue depressors to slightly over shape the scales or put in a wood vise or couple of clamps. Let cool 10-15 minutes and reheat and tweak until you get the shape you want. The whole straightening process takes 20-30 minutes, depending on the warp. While it is clamped and cooling I am doing other things.

There is no formula, it is trial and error, hard to screw it up. It is easier than it sounds.