Push the steel mandrel out of the rivet some, put a dollup of 5200 in the shank and after the shank pops, some more in the end. That should seal the steel from air and water as good as it can be sealed.
As far as the live well, a cooler with a aerator works well and is removable if the family just wants to tool around the lake. Check out and search on GON, Kitch..