@Robh,
i can fully understand this and the hours in debug and checking etc. it all does add up. and why my self and many others are hoping you can get to the end goal.
I have learned to supply yourself some kind off fallback for every c or c++ lib you write. For example
the grotius scurve engine is a quite complicated code. To test changes i have a test suite. Without this,
everything becomes way more difficult.
Off course i hope to reach the end goal for us all.
you need to open up a beer tab for us to tip into! 
Yeahh.
i my self have done many builds over the years on linuxcnc,
its all big iron stuff converted, with new AC servos etc etc.
machiens are 3+4 axis mills, 5 axis mill,
to lathes with single and twin turrets, from small 42mm spindle bore to 600mm swing over the bed.
So very experienced !!
what would be intresting is to see what the difference is on a tool path like trochoidal milling or surfacing , looks promasising in the 2D already.
The advantage for trochoidal milling should be in the scurved velocity profile doesn't it?
Take a look at the cavaliercontours c++ lib on github. When the look ahead works, i will code a sample for this.
This lib can provide us with nice toolpath's. The procedure is as follows:
1. Input the ammount of "n" look ahead lines into the cavaliercontours lib.
2. Offset the open contour to one side with a offset value, given 0.01mm
3. Offset the the offsetted contour back onto the original path. The result is a contour with arc shaped corners.
many thanks for taking on such a task and getting so far along with it.
I had paused the project for a while. But i hope to finish it coming time.