I am currently struggling with some similar issues and may do a full post on my situation. I think it sounds like you may have the same problem that I do where you are looking at it like a cliff where I'm either "retired and never working again" or continuing my current job indefinitely...
I believe the wedge of death was intentional by the author, otherwise it is basically doing the same thing as firecalc. There is a thread over on Mr Money Mustache where the author takes enhancement requests. (He hasn't done the one I'd like to see where the wedge shows the likelihood of death...