Where the hell do I turn off this option, so Ill rest 8 hours always?

The options-gameplay menu.

I checked there many times, I simply dont see any option to turn it off!
I dont believe that the patch 2.01 too kaway the option, but thats the only thing difrent from last time I played.

Thats odd. Have you tried with the config file?

Ok... this is strange, I turned off the option called: "Heal party on rest".
Now I did that before and heres way I thought it didnt help:
It does make you rest only 8 hours when you rest outdoors by pressing the "z" button, but while resting in an inn its still resting until Im fully healed... couple of days. When I tryed that before I checked it at an inn, now I checked it outdoors also.
This is very strange...

Ha ha! I remember when my characters slept for about *50 DAYS* with the "rest untill fully healed" turned on.

I vaguely remember this issue comming up once before.

If you sleep while someone's poisoned, then yes; it'll take until Christ is reborn for you to heal.

The answer here is to check the icewind.ini file. And find the variable that's named something like "rest_until_healed", and set it equal to "0" instead of "1".

After that, reinstall the game.

Bugged.