A Subtle Pawn Endgame

I present here the result of a recent deep analysis I did on a position from one of my own games.  It was a pawn endgame that occurred in one of the variations, and white was clearly trying to save themselves.  

The goal: find the best chance for white to draw.

Think through some ideas yourself as you watch, and look at the alternative variations as well (with my comments) -- they are no less instructive than the mainline.

Enjoy!

If you have feedback and possibly improvements to some of the lines, I warmly welcome your suggestions!