Joe,
The giant slide had so much down time. If there was rain, mist, or fog, the slide was closed. If the wind direction was blowing mist from the 150 foot tall Lake Charles fountain toward the slide, it was closed. Even high humidity in the summer could cause the slide to close. There is a ride crew photo in one of my KD employee yearbooks where each crew member is holding a placard stating every reason why the slide was closed that day!
The Dolphin show started with 2 dolphins. They later expanded the show to include 1-2 sea lions in the performance (The 2 dolphins performed in part of the show and the sea lion(s) performed in the other part).
Sometime in the late 1980's, one of the dolphins that season gave birth at the park to a baby dolphin and they named her "KD" (Sounded like Katy).

A month or so later, the baby died from a bacterial infection.

The investigation found that the show facility's water filtration system was faulty and caused the bacteria to build up in the water. Because of that issue and the, then recently passed U.S. Marine Mammal Act; Kings Dominion stopped having the dolphins perform at the park. They fixed the filtration system and the few remaining years of operations featured just 2 seas lions in the show performance.
Keep in mind that Kings Dominion contracted with a marine mammal based entertainment company, located somewhere on the central Gulf coast, to provide the dolphins and sea lions used in the performance as well as their trainers. KD provided the facilities.
Yes, the pool was about 40 feet in diameter and about 10-12 feet deep. There were 2 small pens (10' by 18'), on either side of the trainer's "house/green room", to hold the dolphins/sea lions overnight. The trainer's "house" had 2 floors; the upper floor was for the trainers to shower/change/rest between shows. The lower floor housed the water filtration system and the freezers for the fishes to feed the dolphins/sea lions.
Even though the facility received a major overhaul during the Paramount years for a stage show, the park kept 30%-35% of the original pool retaining wall to support the front of the current stage. The current, center front section of wall that holds up the stage floor for the "All Wheels Sport" show was once part of the retaining wall for the dolphin pool! Use your imagination and follow the the curve of the wall until it comes to a full circle and you have the size of the original pool.
Again, Kings Dominion was not in the Zoo/Marine Mammal business. The dolphin/sea lions and their trainers were provided by a contracted 3rd party company. The African Animals in Wild Animal Safari and their caretakers were provided by a 3rd party company under contract to the park.
All Kings Dominion did was construct the facilities/animal habitats, based on the 3rd party company's requirements. The park just provided the show ushers/usherettes and the monorail crew for the Wild Animal Safari.
Wiki has some interesting history about the Wild Animal Safari company. In its heyday, (1970's - early 1990's), there were 5 Wild Animal Safari parks across the U.S. (Two of which were in the Family Leisure/Taft/KECO park chain | Kings Dominion and Kings Island). They also had parks in Texas and California as well as their original park in central Florida. Now, only the original park in central Florida exists and is still an drive-through attraction.