Help with Bilstein HD Circlip Position

[Newbie Alert!!]

I have a 97 R Type with a shot suspension. It is a former SpecMiata car. The ride heights: LF: 13.75" LR: 10.5" RF: 14.0" RR: 10.388". The Bilsteins aren't leaking, but the ride is punishing and every pothole kills the car by degrees. I'd like to upgrade the suspension with a complete NB Hard Sport setup, but I have four unanswered questions that someone here many know the answers to:

1) What is the stock ride height of a 97R?
2) What is a reasonable amount to lower the spring perches to provide good street ride and beginner AutoX capabilities with bias toward oversteer?
3) Can the circlip grooves on the Bilsteins be cut by a DIYer [free] or only by Bilstein [$72: rebuild = $65 + circlip groove $7]?
4) Where can I find a relatively simple tutorial which shows the relationship between shock compression/rebound rates and spring rates?

Too many questions, I know but I got hours into finding the answer to these questions and haven't found answers yet.

Thanks!
Gary