I had the exact same situation years ago. My Fraidy cat wasn't afraid at all of my little two lb. peke-a-poo Charmin and beat her up constantly to the point where Charmin would run under our bed and pee on herself. Then Fraidy peed on our bed and the stove top. That did it. As much as I loved Fraidy, I rehomed her. Our vet and I did everything we could to change her behavior and if Clomicalm was around then, I certainly didn't know about it. My next door neighbor loved her so Fraidy went to live w/her and the day that she took her, Fraidy slapped me in the face so hard, it was as though I was slapped by a human! So I knew that I did the right thing. I checked on her every day for a while but Fraidy adapted so well into her new home that any guilt that I had quickly disappeared. I'm not suggesting that you rehome your cat, just that I can sympathize w/you and let you know what solution worked for me.