The Endgame Tactician: dktransform's ending

This is an exciting ending played by my friend dktransformation. I think it's practical and it contains interesting positions, mistakes, and nuggets of wisdom that we can learn from. I hope you enjoy. Please feel free to ask questions, offer alternatives, or disagree.

 Note:

• Click on "Move List" to see possible variations.
• Symbols like =, +=, +/-, ??, and ! are briefly explained here.
• They were playing at 10" + 4" time. That means only 4 seconds per move!