Are there any books that teach navigation with a combination PNA and paper based approach?

A small suggestion. "safety glides" here

http://faculty.chicagobooth.edu/john....htm#maccready

You have to understand what the PNA is saying. They typically compute glides that are way, way too optimistic for safety use. Do not set mac cready zero and think if you're above that you're safe.

The approach you're using is good. Use the standard rules of thumb, develop the mark I eyeball, learn the terrain by heart, and eventually cross check with a PNA that you really understand. Better to get back a few times ridiculously high than to scare yourself once. And even so, remember that four or five clicks with Russian Roulette doesn't make it safe. You're planning for the worst, not the average, and not "I got away with it last time so it must be ok."

John Cochrane