I've looked into this and Rotenone is probably your best option here is an article on it. https://www.noble.org/ag/wildlife/rotenone/
Here a couple years ago I got into a quest for Humpy's and the conditions you've described are exactly what grows them. Odds are according to what I read conditions will continue even if they drain it. Imbalance, lack of predation (or enough to allow sunfish to exceed) are kinda similar to aquarium environments. Some species of sunfish spawn the entire warm water season according to one article. If nothing else it's got to be a good bait pond. Love those greenies when their fins get striped, it's mesmerizing to watch them in the water
All lakes raise a foot when I step in the boatskinner80 LIKED above post