I'm so sorry @Patrice, for all the "magic" of modern software, nothing can create focus where focus doesn't exist. This photo is what it is, I'm afraid.
All I can suggest is to add a Hue/Saturation layer. Don't touch the "Master" channel. On the Reds channel move the Saturation slider to -100. Then on all the remaining channels (Yellow thru Magenta) move their Lightness sliders to +100.
Sometimes 16-bit is very necessary ... but most of the time 8-bit is adequate.
16-bit is only necessary for photos that will require significant tonal adjustments in Photoshop. The most common of these is backlit hazy photos that need black balance, as you'll learn in the Advanced Levels Class (please don't wait too long).
It's foolish to edit everything in 16-bit.
It's called "Large Document Format" in the file format list in the save dialog. In my version, it's the second option, right under PSD. Are you sure you don't have it?
Why are you in 16-bit?
I don't have a solution for this photo at all, sorry. The background behind the hair is just too varied.
May I see a 100% crop of the area at the top of Dad's head?