Hello TurboRx, change the container into one with drain holes. Or if you really like that container, then just use it as cache pot to catch excess water, but the main container for the plant must have drain holes. Always allow the excess water to drain away after watering, never let it sit in water.
Peace lily does not like direct sun. So bright light and warmth, that is better for it. Do not fertilize yet, it is in such big stress. There is still potential for recovery, so try to change the container, improve the media, position in better bright light area and be very patient. Avoid overwatering. It would be nice if you can put a thin layer of pumice at the topmost surface, that way it will discourage fungus gnats. Be very patient, it takes time, especially if the roots were compromised.
This is an old file photo of mine, when I had to try and recover my peace lily, badly fried when my hubby thought it can take our extremely hot and dry garden. To all intents it was too dead looking, thankfully I got back in time, and Fall season has started, so temps were cooling down. Had to step up watering to revive the rhizome. It took a long time, and I have to protect it from winter, so it stayed indoors, water reduced a bit, but soil remains damp, container with drain holes...it did take a long time..but it came back...so I feel your plant still has a potential. Be careful when you repot, try not to disturb the roots too much.