I've done some stub acme and buttress threading on parts for oil and gas, too long back to recall any specifics but
it looks like you need "J profile" threading insert, J profile has radius on root and crest.
Quick search found PDF catalog below.
As for end of the threads you have circled in red, it appears to be just dissipating extension at taper angle of threads.
At 1.47 degrees taper, that would likely extend far beyond given length so using fading in Fusion would produce code to pull out at another angle at end of each pass.
If you don't use fading, you'll end up with "V" shaped groove at the end of threading cycle.
On your sketch I see threads are broken in sections, giving length of usable engagement, front chamfer angle and exit length. Without actual numbers that apply to each section I can't make out final configuration but it seems to be typical threading operation using specific insert cutting at required taper and fading out at the end.
To produce tapered threads, you need to model taper and use it as geometry in threading operation.
