CCL, I'm heartbroken as I'm reading this, I'm so sorry things don't work out well.

Well, maybe it's true and they just need more time, but I can understand your concern so well! After what has happened to your wrist, it's no surprise that you're fearing for your resident cats!

And since you think Mr. Magoo is displaying alpha male behavior, I really wonder if his behavior will ever change. Well, I don't have much experiences with introducing one cat to another (the only time I did it was when I brought home Lily, and luckily that worked great), but I would think there would be a bigger change if Mr. Magoo's agression came from fear or confusion. Obviously it's not like that and he wants to dominate, and this could be a constant problem.

I wonder why he never behaved like that in the shelter? You have described him as a very friendly and loving cat there.

I agree it would be hard and sad to bring him back there, it would be nice if he could find a good place as a single cat, or in a household where he could have an extra room.

I really don't envy you for the situation you're in, but please don't feel you have failed!! You did what you thought was the best for him, but like with every living creature, some things are unpredictable. I'm so sad for you!

One other idea - what about getting in touch with local media - your regional TV station or newspaper. Nothing like a heart-wrenching story to motivate an animal lover!!!
I think that's a good idea! Here in Germany, we have shows on tv where they're introducing pets that are looking for a new home.