Well first of all Kudos to you and your efforts........
The goldie can stay in the 30 for awhile as long as you keep up with the waterchanges. He's not going to be nearly as active as he should be in his health.
The blindness is most likely permanent (never heard of any animal getting their sight back).
I honestly wouldn't give him more than 2-3 weeks though. If he is blind, finding food will be hard for him, not mention swimming. It might be better to euthanize him and save him the misery.
I would not put him with any other fish if he does begin healing. You really cant tell what all infections or other diseases he could possibly have. You wouldn't want to infect your other fish.
Depending on the cichlid it could work but I'm guessing they will need a slightly larger tank in the least. A more knowledgeable cichlid keeper can help you there once you get him ID'd.
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For in much wisdom [is] much grief: and he that increaseth knowledge increaseth sorrow.

Member of the AGA (Aquatic Gardner's Association)
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