I got tears in my eyes when I read your post. I am so sorry....Such a difficult and painful decision but it does sound like it’s the best for all. Years ago we had to rehome one of our kitties because of aggression issues. We had four cats at the time and they got along quite well. Then there was an incident between two of the cats and something switched and this kitty could never get over it and became more and more aggressive and stalked the other kitties and even us. I was bitten several times when I would just walk by him. We were so lucky in that our oldest son, who was with me when we got him from the Humane Society as a tiny kitten, was able to take him in and he lived to be an old kitty. Had he not taken him we would have had to rehome elsewhere as it really was unfair to him and especially the other cats.
Sometimes, despite our best efforts, things happen that we are unable to fix. It’s so hard but rehoming is, indeed, sometimes the best choice. You are making a wise, kind, brave and loving decision.
Sending you hugs during this painful time. Keep us updated as you can.