AB
I am so terribly sorry you are going through the pain of losing Ziva, and the angst of second-guessing your decision! In all honesty, I have to say that I, personally, would have tried the crate and rotate or other means of separation, before making an irrevocable decision. However, this was a rescue Fila. Additionally, the situation reminds me of what happened to an acquaintance of mine on a Great Dane forum. She was a highly experienced dog owner and apprentice professional trainer. She adopted a beautiful GD bitch, who unfortunately came with quite a lot of 'baggage'. Judging from videos, my acquaintance's training was impeccable, but the dog had completely bizarre and unpredictable outbursts in which she growled and snapped at family members -- actually biting them on a number of occasions. My acquaintance worked committedly with this dog to help her overcome her 'demons', and refused to consider the option of releasing her spirit. Then after a couple of years of hard and diligent training and work, the dog was lying on the sofa with the teenage daughter -- perfectly relaxed -- and suddenly attacked the girl, biting her face so seriously it has left scars (not to mention the emotional ones). My acquaintance was devastated and had her dog put to sleep. As hard as it was -- because of course the dog was beautifully obedient and hopped up on the euthenisation table and lay down -- my acq. was heartbroken, but relieved her pup's spirit had been released from its demons, and regretted that she had not made the decision earlier.
So you have undoubtedly averted a tragedy waiting to happen! I know that many rescues become wonderful family members and companions, but some of them come with history that is difficult, or sometimes impossible to overcome. Walk through the dark forest with serenity and peace.....