Small confined ponds and large bodies of water are very different in how species perform. What may work in the "wild" often doesn't work in a pond environment...

Just two BG can lead to an over populated mess if there are no bass present. If those two BG are a male and a female, you will almost undoubtedly have 1,000's of BG within a year or two without predation. CC are predators, but their mouth size limits their ability to prey on BG and thus they are not good predators at controlling BG.

Bullheads are definitely more common in the piedmont and coastal areas of NC, but they are still rather common in the more mountainous areas of NC and other states. Yellow bullheads in particularly actually do quite well in habitat associated with SMB and even trout. They just may be not be caught frequently like they would be in a pond environment.

Again, it is important to determine exactly what species you have present in your new pond and if they are reproducing. Until you know what you have, giving you advice on how to proceed is futile. With your pond being on the smaller size, it may be advisable to drain it, treat the small remaining area with hydrated lime to make sure any fish present are dead. Then you can start with a 100% certain clean slate.

Many new pond owners seem to love the idea of just dumping in a little of this and a little of that via bucket stocking. Rarely does this produce a quality fishery. It would be like randomly grabbing a pile of seeds from the store and dumping them into your garden. Will they grow? Most likely, but are they going to produce the quality crops you want, not likely.