I spent a little more time on it this weekend. I'd say I'm about 20% done. This will be an Acrobat form in the final version and two pages. All the math (where possible) will be done for you.
Feedback welcome and suggestions greatly appreciated -- I'm not married to some aspects of the layout. (Or colors.)
It's a whopping 54KB.
[Edit] 4-28 New version down below...