1.You need new version of FSD 3 Rev 775 to see new TU.
2.You can update your console to new kernel version and you don't need to worry about "ruin" your RGHYou have tutorials how to do that and how to make a hacked image.
3.It will be good to update your DL and you not lose your setting in it.Just download new version,put Installer folder on USB flash drive,run default.xex from Xex Menu and you will be promt to update your DL.
4.No you don't need to reformat your hard drive.Just delete your previous FSD folder and copy new version.I hope that you didn't forget how to do this.
BTW.GTA V requires 16203 dash minimum and that's why you can't play the game.