In the interest of actually answering the question: spoke length is a tough one. I'd probably draw out the pattern to scale, come up with a triangle out of that, use a straight spoke length for the base of the triangle, and use some basic trig to figure out how long the rest of the triangle is. Add the other two side lengths together, and add maybe 2mm per twist?

Agree that it's not a high-quality build, but it sure can look nice: