Diana, now that I've had time to sit down and look at the other three questions, I'm having more trouble. I believe it's a nomenclature issue:
1. For number 1, what is the accurate definition that you have been given for "root angle"? I don't find it in my gear books.
2. For number 3, what exactly do you mean by "their threads make equal right angles"? Can you email me a picture? Naturally, this will help me solve number 4 as well.
Sorry about the delay...