Hello shaman. I am very sorry to hear about the situation you have going on. Something like an eye dropper is really about your only hope that I can think of. If your bird is blind in both eyes though it has very little chance of surviving let alone thriving. Watching a creature suffer is always rough, at some point you have to make the decision as to whether or not this bird will have a chance at life. You can keep it alive yes, but is it LIVING? I cannot tell you what to do but failure to thrive is thing.
Now to more directly address your question. You need to give it small amounts of water frequently as opposed to moderate water intermittently if you want it to stay alive. Yes your concern about over watering is an issue, that you are aware of it means you will more than likely not drown the chick but you will be needing to really nurse this bird and spend a lot of time taking care of it. There was famously a rooster who lived for several years without a HEAD. If you have the patience and attention to detail you can do it. Fermented chick feed makes eating easier for the bird and for you to feed it. Best Wishes.
