Minecraft Java Edition – Spectator Mode Invisibility Glitch Solution

"fixing" a corrupt file for the purpose of minecraft is near impossible.

If you wish to try and salvage your save and read what is left:

1. change the extension of the document back to .dat
2. follow SevenSidedDie's advice and use NBT Explorer to parse the file

if NBT cannot read anything legible, the file may be beyond repair.

if NBT can read it, you can copy information from it to a new save (such as inventory items / settings)

I know this isn't excactly what you want to hear but I hope it helps, Good luck :)

An overworld just disappearing like that is highly unlikely. If I had to guess, your son created a new portal after exploring the nether, which put him in a completely different part of the same overworld. To get back to spawn, you could try a few things (which are especially easy in creative mode):

• Type /kill in the console: You'll die, and respawn where you were when entering the world.
• Type /tp [playername] 0 70 0: This will teleport you to the center of the world, a little above ground level.
• Use a compass: If commands aren't at your disposal, you can always just grab a compass and follow it back to spawn.