Ok guys, I've just tested this, as you are probably aware, I had the problem with loading any save file except for one. I once started the quest The Murders in Byways by accident, without talking to the person that gives the contract. There was a small glitch there, quest advanced and Geralt told the peasants that it's safe even though ghouls were still around. I then moved on as the monster was too strong for me to kill. Later on I was in Novigrad and I was attacked by some thugs hired by a preacher I humiliated before, I killed them and shortly after my game crashed. It happened each time I wanted to load 9 of my 10 saves. One save was working. It was outside of Novigrad (don't know if it matters) and I could play the game fine up until I decided to save. Then I had the crash again, even after deleting all of the files except for the working one.
I read what eeegamer posted about a possible solution and I tried it (credits to DerK4ter also). So what I did is: I finished The Murders in Byways quest. Killed the monster, went back to talk to peasants, fast traveled to report the quest to the contract giver, saved my game. Tried to load the save I have just made. WORKED. Skeptical about it, I've made another save file and loaded it. WORKED. To test it further, I loaded the Checkpoint save that the game made automatically (they crashed before too) and.., WORKED. As a final test I loaded the Auto Save right after I fast traveled to the contract giver (Oredon village). WORKED.
So to sum up, as of now, the saves worked thanks to finishing the mission The Murders in Byways ALL of the saves I made after the mission and all Auto saves and checkpoint saves WORKED. My manual saves WORKED. I can play again normally. Thanks to eeegamer and DerK4ter again. For now my game is back to normal. I hope I'm not being overly happy too soon. I'll update on my progress.