great pics there H, you've done well.

Yes measure from the crown of the fret to the string, but the pics are good and allow us to see the distances involved.

Others may correct me but it looks a bit tall at the first fret, you could possibly take some meat off the bottom of the nut and drop it a bit more, but if you can live with it then fine. Also I assume the neck is just press fitted in the body, so things may change a little after clamping and gluing....

Your plan is good, sanding and headstock shaping, good idea to practice first if you are new to coping saws, but if you are careful and stay a bit outside the line of the cut, and finish with files/sanding for the final profile, you should be fine.

Good work, enjoy