So, I still have my dear NWN2 installed, up to date as far as I know, no aggressive mods or whatsoever. I decided to dust it off out of boredon, and found out the number keys are swapping my skill tabs, instead of using the skill assigned to the number... I can't find out how it happened and how to fix it. Help, please?

I'm not sure what you mean by swapping your skill tabs, but you could try removing your nwn2player.ini file from C:\Users\UserName\Documents\Neverwinter Nights 2
When you restart the game it will create a new default one, and see if that fixes it.

You can also check if your CTRL key is stuck or not. That sometimes weirdly happens with those old games.