Good luck
Paul,
Good luck to you as you deal with the choices. I got Bonnie Klein's tape a while back and found it to be useful. From your point of view it might be extremely valuable. It shows a homemade threading jig that you could probably duplicate at considerable savings. I have not seen Bonnie's instructions with her threading jig, so I won't comment on their value. The instructions with BWT's jig I believe are Willard Baxter's notes on turning an acorn box.
I have not yet found a satisfactory source for numbers you need to make the transition from the threads inside the lid to the threads outside the bottom. Some say add a certain number and that number does not compute for me. After a few more trial and error sessions I may identify them and share them with the forum.