Good point. My feedback is that the details in Detail D drawing is not sufficient to contrain the sketch. What do you think?
You can always add dimensions\constraints to fully constrain even if you only have "ballpark" numbers for now.
For example - the fillet groove would be cut using a standard cutter (much like the one you are trying to model) and/or ground with a standard radius - so you can start to fill in the missing information.
Surely someone else manufactures these tools, can you measure a competitors product?
But the question of only that radius brings me back to the Coil feature - does it really product the profile the actuall manufacturing tool creates? (this gets into an old and long discussion about sweeping a solid along a path rather than simply a 2D profile)