Wow. Sometimes I forget this is still Earth, human-filled and all. I'd say just adopt him yourself. Sorry if it seems like I'm being ignorant in thinking you can easily handle the task, but its the best I've got. I wonder what will happen with the poor dogs once you leave, though.
Honestly, I think the only way you can ensure that the cat's life improves is to try to keep him yourself. It sounds like he gets along with your cats okay. It might be a really fast adjustment for him, and I'm sure the move would be stressful. I don't think it would be any more difficult to find a new place if you have three cats instead of two.
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