If he is this scared, I wouldn't put any bird in with him. And what can happen is when you put him back in with the flock, and he is scared like this, they can attack him. They will know he is not fit for the flock. I think this bird may need to be on his own for the rest of his days.
If this were my bird, I would let him adjust by himself for a couple weeks, learning to get around with one eye. Then I would take my most easy going female, like the one you tried putting in with him and keep her with him. After he is comfortable with his disability, he will probably welcome a friend. But I would only keep just one with him.
If this were my bird, I would let him adjust by himself for a couple weeks, learning to get around with one eye. Then I would take my most easy going female, like the one you tried putting in with him and keep her with him. After he is comfortable with his disability, he will probably welcome a friend. But I would only keep just one with him.