Sometimes dogs like this do have genetic rage issues, and when they are triggered there isn't much you can do to stop the reaction.
I think you did the best thing. This dog needs to be worked with and re-evaluated before sending it anywhere. Perhaps she needs to go to a home with no other pets or children. Just one grumpy old man who would love to love on her and not stress her out.
I wish you all the luck in finding a better match.