First of all, cocking distance will never be equal to firing pin travel. By using a little common sense you should realize that. If you would actually physically measure it, you would see. How I gain firing pin travel is a trade secret. Like I said before, it took me 3 years to figure this out and I work on hundreds of actions a year. When you get that many under your belt, you'll have it figured out too.
I was never any good at algabra either, that's why I put the task to someone who is. Ottesons formula may be correct, but the numbers he uses are not. Like I said before the data he collected does not match what I have collected over 10 years and hundreds of actions. Garbage in-garbage out, if the numbers are not right, the end result is not right. Just be cause it's published and well respected, does not mean it's accurate.